version 2, including all changes.
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FLEX |
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!!!FLEX |
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NAME |
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SYNOPSIS |
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OVERVIEW |
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DESCRIPTION |
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SOME SIMPLE EXAMPLES |
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FORMAT OF THE INPUT FILE |
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PATTERNS |
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HOW THE INPUT IS MATCHED |
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ACTIONS |
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THE GENERATED SCANNER |
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START CONDITIONS |
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MULTIPLE INPUT BUFFERS |
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END-OF-FILE RULES |
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MISCELLANEOUS MACROS |
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VALUES AVAILABLE TO THE USER |
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INTERFACING WITH YACC |
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OPTIONS |
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PERFORMANCE CONSIDERATIONS |
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GENERATING C++ SCANNERS |
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INCOMPATIBILITIES WITH LEX AND POSIX |
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DIAGNOSTICS |
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FILES |
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DEFICIENCIES / BUGS |
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SEE ALSO |
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AUTHOR |
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---- |
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!!NAME |
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flex - fast lexical analyzer generator |
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!!SYNOPSIS |
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__flex [[-bcdfhilnpstvwBFILTV78+? -C[[aefFmr] -ooutput |
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-Pprefix -Sskeleton] [[--help --version]__ ''[[filename |
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...]'' |
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!!OVERVIEW |
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This manual describes ''flex,'' a tool for generating |
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programs that perform pattern-matching on text. The manual |
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includes both tutorial and reference sections: |
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Description |
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a brief overview of the tool |
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Some Simple Examples |
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Format Of The Input File |
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Patterns |
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the extended regular expressions used by flex |
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How The Input Is Matched |
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the rules for determining what has been matched |
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Actions |
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how to specify what to do when a pattern is matched |
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The Generated Scanner |
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details regarding the scanner that flex produces; |
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how to control the input source |
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Start Conditions |
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introducing context into your scanners, and |
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managing |
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!!DESCRIPTION |
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''flex'' is a tool for generating ''scanners:'' |
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programs which recognized lexical patterns in text. |
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''flex'' reads the given input files, or its standard |
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input if no file names are given, for a description of a |
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scanner to generate. The description is in the form of pairs |
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of regular expressions and C code, called ''rules. flex'' |
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generates as output a C source file, __lex.yy.c,__ which |
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defines a routine __yylex().__ This file is compiled and |
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linked with the __-lfl__ library to produce an |
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executable. When the executable is run, it analyzes its |
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input for occurrences of the regular expressions. Whenever |
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it finds one, it executes the corresponding C |
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code. |
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!!SOME SIMPLE EXAMPLES |
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First some simple examples to get the flavor of how one uses |
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''flex.'' The following ''flex'' input specifies a |
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scanner which whenever it encounters the string |
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'' |
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%% |
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username printf( |
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By default, any text not matched by a ''flex'' scanner is copied to the output, so the net effect of this scanner is to copy its input file to its output with each occurrence of ''pattern'' and the ''action.'' The '' |
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Here's another simple example: |
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int num_lines = 0, num_chars = 0; |
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%% |
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n ++num_lines; ++num_chars; |
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. ++num_chars; |
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%% |
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main() |
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{ |
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yylex(); |
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printf( |
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This scanner counts the number of characters and the number of lines in its input (it produces no output other than the final report on the counts). The first line declares two globals, yylex()__ and in the __main()__ routine declared after the second __ |
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A somewhat more complicated example: |
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/* scanner for a toy Pascal-like language */ |
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%{ |
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/* need this for the call to atof() below */ |
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#include |
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This is the beginnings of a simple scanner for a language like Pascal. It identifies different types of ''tokens'' and reports on what it has seen. |
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The details of this example will be explained in the |
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following sections. |
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!!FORMAT OF THE INPUT FILE |
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The ''flex'' input file consists of three sections, |
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separated by a line with just __%%__ in it: |
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definitions |
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%% |
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rules |
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%% |
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user code |
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The ''definitions'' section contains declarations of simple ''name'' definitions to simplify the scanner specification, and declarations of ''start conditions,'' which are explained in a later section. |
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Name definitions have the form: |
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name definition |
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The |
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DIGIT [[0-9] |
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ID [[a-z][[a-z0-9]* |
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defines |
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{DIGIT}+ |
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is identical to |
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([[0-9])+ |
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and matches one-or-more digits followed by a '.' followed by zero-or-more digits. |
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The ''rules'' section of the ''flex'' input contains a |
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series of rules of the form: |
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pattern action |
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where the pattern must be unindented and the action must begin on the same line. |
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See below for a further description of patterns and |
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actions. |
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Finally, the user code section is simply copied to |
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__lex.yy.c__ verbatim. It is used for companion routines |
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which call or are called by the scanner. The presence of |
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this section is optional; if it is missing, the second |
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__%%__ in the input file may be skipped, |
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too. |
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In the definitions and rules sections, any ''indented'' |
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text or text enclosed in __%{__ and __%}__ is copied |
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verbatim to the output (with the %{}'s removed). The %{}'s |
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must appear unindented on lines by themselves. |
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In the rules section, any indented or %{} text appearing |
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before the first rule may be used to declare variables which |
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are local to the scanning routine and (after the |
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declarations) code which is to be executed whenever the |
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scanning routine is entered. Other indented or %{} text in |
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the rule section is still copied to the output, but its |
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meaning is not well-defined and it may well cause |
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compile-time errors (this feature is present for |
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''POSIX'' compliance; see below for other such |
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features). |
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In the definitions section (but not in the rules section), |
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an unindented comment (i.e., a line beginning with |
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!!PATTERNS |
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The patterns in the input are written using an extended set |
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of regular expressions. These are: |
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x match the character 'x' |
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. any character (byte) except newline |
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[[xyz] a |
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Note that inside of a character class, all regular expression operators lose their special meaning except escape ('') and the character class operators, '-', ']', and, at the beginning of the class, '^'. |
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The regular expressions listed above are grouped according |
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to precedence, from highest precedence at the top to lowest |
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at the bottom. Those grouped together have equal precedence. |
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For example, |
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foo|bar* |
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is the same as |
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(foo)|(ba(r*)) |
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since the '*' operator has higher precedence than concatenation, and concatenation higher than alternation ('|'). This pattern therefore matches ''either'' the string ''or'' the string '' |
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foo|(bar)* |
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and to match zero-or-more |
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(foo|bar)* |
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In addition to characters and ranges of characters, character classes can also contain character class ''expressions.'' These are expressions enclosed inside __[[:__ and __:]__ delimiters (which themselves must appear between the '[[' and ']' of the character class; other elements may occur inside the character class, too). The valid expressions are: |
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[[:alnum:] [[:alpha:] [[:blank:] |
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[[:cntrl:] [[:digit:] [[:graph:] |
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[[:lower:] [[:print:] [[:punct:] |
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[[:space:] [[:upper:] [[:xdigit:] |
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These expressions all designate a set of characters equivalent to the corresponding standard C __isXXX__ function. For example, __[[:alnum:]__ designates those characters for which __isalnum()__ returns true - i.e., any alphabetic or numeric. Some systems don't provide __isblank(),__ so flex defines __[[:blank:]__ as a blank or a tab. |
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For example, the following character classes are all |
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equivalent: |
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[[[[:alnum:]] |
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[[[[:alpha:][[:digit:]] |
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[[[[:alpha:][[0-9]] |
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[[a-zA-Z0-9] |
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If your scanner is case-insensitive (the __-i__ flag), then __[[:upper:]__ and __[[:lower:]__ are equivalent to __[[:alpha:].__ |
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Some notes on patterns: |
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- |
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A negated character class such as the example |
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will match a newline'' unless |
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'' |
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- |
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A rule can have at most one instance of trailing context |
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(the '/' operator or the '$' operator). The start condition, |
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'^', and |
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The following are illegal: |
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foo/bar$ |
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Note that the first of these, can be written |
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The following will result in '$' or '^' being treated as a |
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normal character: |
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foo|(bar$) |
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foo|^bar |
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If what's wanted is a |
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foo | |
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bar$ /* action goes here */ |
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A similar trick will work for matching a foo or a bar-at-the-beginning-of-a-line. |
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!!HOW THE INPUT IS MATCHED |
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When the generated scanner is run, it analyzes its input |
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looking for strings which match any of its patterns. If it |
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finds more than one match, it takes the one matching the |
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most text (for trailing context rules, this includes the |
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length of the trailing part, even though it will then be |
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returned to the input). If it finds two or more matches of |
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the same length, the rule listed first in the ''flex'' |
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input file is chosen. |
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Once the match is determined, the text corresponding to the |
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match (called the ''token)'' is made available in the |
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global character pointer __yytext,__ and its length in |
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the global integer __yyleng.__ The ''action'' |
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corresponding to the matched pattern is then executed (a |
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more detailed description of actions follows), and then the |
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remaining input is scanned for another match. |
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If no match is found, then the ''default rule'' is |
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executed: the next character in the input is considered |
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matched and copied to the standard output. Thus, the |
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simplest legal ''flex'' input is: |
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%% |
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which generates a scanner that simply copies its input (one character at a time) to its output. |
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Note that __yytext__ can be defined in two different |
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ways: either as a character ''pointer'' or as a character |
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''array.'' You can control which definition ''flex'' |
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uses by including one of the special directives |
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__%pointer__ or __%array__ in the first (definitions) |
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section of your flex input. The default is __%pointer,__ |
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unless you use the __-l__ lex compatibility option, in |
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which case __yytext__ will be an array. The advantage of |
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using __%pointer__ is substantially faster scanning and |
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no buffer overflow when matching very large tokens (unless |
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you run out of dynamic memory). The disadvantage is that you |
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are restricted in how your actions can modify __yytext__ |
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(see the next section), and calls to the __unput()__ |
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function destroys the present contents of __yytext,__ |
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which can be a considerable porting headache when moving |
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between different ''lex'' versions. |
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The advantage of __%array__ is that you can then modify |
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__yytext__ to your heart's content, and calls to |
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__unput()__ do not destroy __yytext__ (see below). |
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Furthermore, existing ''lex'' programs sometimes access |
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__yytext__ externally using declarations of the |
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form: |
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extern char yytext[[]; |
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This definition is erroneous when used with __%pointer,__ but correct for __%array.__ |
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__%array__ defines __yytext__ to be an array of |
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__YYLMAX__ characters, which defaults to a fairly large |
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value. You can change the size by simply #define'ing |
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__YYLMAX__ to a different value in the first section of |
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your ''flex'' input. As mentioned above, with |
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__%pointer__ yytext grows dynamically to accommodate |
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large tokens. While this means your __%pointer__ scanner |
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can accommodate very large tokens (such as matching entire |
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blocks of comments), bear in mind that each time the scanner |
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must resize __yytext__ it also must rescan the entire |
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token from the beginning, so matching such tokens can prove |
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slow. __yytext__ presently does ''not'' dynamically |
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grow if a call to __unput()__ results in too much text |
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being pushed back; instead, a run-time error |
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results. |
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Also note that you cannot use __%array__ with C++ scanner |
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classes (the __c++__ option; see below). |
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!!ACTIONS |
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Each pattern in a rule has a corresponding action, which can |
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be any arbitrary C statement. The pattern ends at the first |
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non-escaped whitespace character; the remainder of the line |
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is its action. If the action is empty, then when the pattern |
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is matched the input token is simply discarded. For example, |
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here is the specification for a program which deletes all |
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occurrences of |
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%% |
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(It will copy all other characters in the input to the output since they will be matched by the default rule.) |
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Here is a program which compresses multiple blanks and tabs |
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down to a single blank, and throws away whitespace found at |
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the end of a line: |
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%% |
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[[ t]+ putchar( ' ' ); |
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[[ t]+$ /* ignore this token */ |
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If the action contains a '{', then the action spans till the balancing '}' is found, and the action may cross multiple lines. ''flex'' knows about C strings and comments and won't be fooled by braces found within them, but also allows actions to begin with __%{__ and will consider the action to be all the text up to the next __%}__ (regardless of ordinary braces inside the action). |
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An action consisting solely of a vertical bar ('|') means |
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Actions can include arbitrary C code, including |
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__return__ statements to return a value to whatever |
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routine called __yylex().__ Each time __yylex()__ is |
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called it continues processing tokens from where it last |
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left off until it either reaches the end of the file or |
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executes a return. |
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Actions are free to modify __yytext__ except for |
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lengthening it (adding characters to its end--these will |
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|
407 |
overwrite later characters in the input stream). This |
|
|
408 |
however does not apply when using __%array__ (see above); |
|
|
409 |
in that case, __yytext__ may be freely modified in any |
|
|
410 |
way. |
|
|
411 |
|
|
|
412 |
|
|
|
413 |
Actions are free to modify __yyleng__ except they should |
|
|
414 |
not do so if the action also includes use of __yymore()__ |
|
|
415 |
(see below). |
|
|
416 |
|
|
|
417 |
|
|
|
418 |
There are a number of special directives which can be |
|
|
419 |
included within an action: |
|
|
420 |
|
|
|
421 |
|
|
|
422 |
- |
|
|
423 |
|
|
|
424 |
|
|
|
425 |
__ECHO__ copies yytext to the scanner's |
|
|
426 |
output. |
|
|
427 |
|
|
|
428 |
|
|
|
429 |
- |
|
|
430 |
|
|
|
431 |
|
|
|
432 |
__BEGIN__ followed by the name of a start condition |
|
|
433 |
places the scanner in the corresponding start condition (see |
|
|
434 |
below). |
|
|
435 |
|
|
|
436 |
|
|
|
437 |
- |
|
|
438 |
|
|
|
439 |
|
|
|
440 |
__REJECT__ directs the scanner to proceed on to the |
|
|
441 |
__yytext__ |
|
|
442 |
and __yyleng__ set up appropriately. It may either be one |
|
|
443 |
which matched as much text as the originally chosen rule but |
|
|
444 |
came later in the ''flex'' input file, or one which |
|
|
445 |
matched less text. For example, the following will both |
|
|
446 |
count the words in the input and call the routine special() |
|
|
447 |
whenever '' |
|
|
448 |
|
|
|
449 |
|
|
|
450 |
int word_count = 0; |
|
|
451 |
%% |
|
|
452 |
frob special(); REJECT; |
|
|
453 |
[[^ tn]+ ++word_count; |
|
|
454 |
Without the __REJECT,__ any __REJECT's__ are allowed, each one finding the next best choice to the currently active rule. For example, when the following scanner scans the token __ |
|
|
455 |
|
|
|
456 |
|
|
|
457 |
%% |
|
|
458 |
a | |
|
|
459 |
ab | |
|
|
460 |
abc | |
|
|
461 |
abcd ECHO; REJECT; |
|
|
462 |
.|n /* eat up any unmatched character */ |
|
|
463 |
(The first three rules share the fourth's action since they use the special '|' action.) __REJECT__ is a particularly expensive feature in terms of scanner performance; if it is used in ''any'' of the scanner's actions it will slow down ''all'' of the scanner's matching. Furthermore, __REJECT__ cannot be used with the ''-Cf'' or ''-CF'' options (see below). |
|
|
464 |
|
|
|
465 |
|
|
|
466 |
Note also that unlike the other special actions, |
|
|
467 |
__REJECT__ is a ''branch;'' code immediately following |
|
|
468 |
it in the action will ''not'' be executed. |
|
|
469 |
|
|
|
470 |
|
|
|
471 |
- |
|
|
472 |
|
|
|
473 |
|
|
|
474 |
__yymore()__ tells the scanner that the next time it |
|
|
475 |
matches a rule, the corresponding token should be |
|
|
476 |
''appended'' onto the current value of __yytext__ |
|
|
477 |
rather than replacing it. For example, given the input |
|
|
478 |
__ |
|
|
479 |
|
|
|
480 |
|
|
|
481 |
%% |
|
|
482 |
mega- ECHO; yymore(); |
|
|
483 |
kludge ECHO; |
|
|
484 |
First yytext__ so the __ECHO__ for the __ |
|
|
485 |
|
|
|
486 |
|
|
|
487 |
Two notes regarding use of __yymore().__ First, |
|
|
488 |
__yymore()__ depends on the value of ''yyleng'' |
|
|
489 |
correctly reflecting the size of the current token, so you |
|
|
490 |
must not modify ''yyleng'' if you are using |
|
|
491 |
__yymore().__ Second, the presence of __yymore()__ in |
|
|
492 |
the scanner's action entails a minor performance penalty in |
|
|
493 |
the scanner's matching speed. |
|
|
494 |
|
|
|
495 |
|
|
|
496 |
- |
|
|
497 |
|
|
|
498 |
|
|
|
499 |
__yyless(n)__ returns all but the first ''n'' |
|
|
500 |
characters of the current token back to the input stream, |
|
|
501 |
where they will be rescanned when the scanner looks for the |
|
|
502 |
next match. __yytext__ and __yyleng__ are adjusted |
|
|
503 |
appropriately (e.g., __yyleng__ will now be equal to |
|
|
504 |
''n'' ). For example, on the input |
|
|
505 |
'' |
|
|
506 |
|
|
|
507 |
|
|
|
508 |
%% |
|
|
509 |
foobar ECHO; yyless(3); |
|
|
510 |
[[a-z]+ ECHO; |
|
|
511 |
An argument of 0 to __yyless__ will cause the entire current input string to be scanned again. Unless you've changed how the scanner will subsequently process its input (using __BEGIN,__ for example), this will result in an endless loop. |
|
|
512 |
|
|
|
513 |
|
|
|
514 |
Note that __yyless__ is a macro and can only be used in |
|
|
515 |
the flex input file, not from other source |
|
|
516 |
files. |
|
|
517 |
|
|
|
518 |
|
|
|
519 |
- |
|
|
520 |
|
|
|
521 |
|
|
|
522 |
__unput(c)__ puts the character ''c'' back onto the |
|
|
523 |
input stream. It will be the next character scanned. The |
|
|
524 |
following action will take the current token and cause it to |
|
|
525 |
be rescanned enclosed in parentheses. |
|
|
526 |
|
|
|
527 |
|
|
|
528 |
{ |
|
|
529 |
int i; |
|
|
530 |
/* Copy yytext because unput() trashes yytext */ |
|
|
531 |
char *yycopy = strdup( yytext ); |
|
|
532 |
unput( ')' ); |
|
|
533 |
for ( i = yyleng - 1; i |
|
|
534 |
Note that since each __unput()__ puts the given character back at the ''beginning'' of the input stream, pushing back strings must be done back-to-front. |
|
|
535 |
|
|
|
536 |
|
|
|
537 |
An important potential problem when using __unput()__ is |
|
|
538 |
that if you are using __%pointer__ (the default), a call |
|
|
539 |
to __unput()__ ''destroys'' the contents of |
|
|
540 |
''yytext,'' starting with its rightmost character and |
|
|
541 |
devouring one character to the left with each call. If you |
|
|
542 |
need the value of yytext preserved after a call to |
|
|
543 |
__unput()__ (as in the above example), you must either |
|
|
544 |
first copy it elsewhere, or build your scanner using |
|
|
545 |
__%array__ instead (see How The Input Is |
|
|
546 |
Matched). |
|
|
547 |
|
|
|
548 |
|
|
|
549 |
Finally, note that you cannot put back __EOF__ to attempt |
|
|
550 |
to mark the input stream with an end-of-file. |
|
|
551 |
|
|
|
552 |
|
|
|
553 |
- |
|
|
554 |
|
|
|
555 |
|
|
|
556 |
__input()__ reads the next character from the input |
|
|
557 |
stream. For example, the following is one way to eat up C |
|
|
558 |
comments: |
|
|
559 |
|
|
|
560 |
|
|
|
561 |
%% |
|
|
562 |
(Note that if the scanner is compiled using __C++,__ then __input()__ is instead referred to as __yyinput(),__ in order to avoid a name clash with the __C++__ stream by the name of ''input.)'' |
|
|
563 |
|
|
|
564 |
|
|
|
565 |
- |
|
|
566 |
|
|
|
567 |
|
|
|
568 |
__YY_FLUSH_BUFFER__ flushes the scanner's internal buffer |
|
|
569 |
so that the next time the scanner attempts to match a token, |
|
|
570 |
it will first refill the buffer using __YY_INPUT__ (see |
|
|
571 |
The Generated Scanner, below). This action is a special case |
|
|
572 |
of the more general __yy_flush_buffer()__ function, |
|
|
573 |
described below in the section Multiple Input |
|
|
574 |
Buffers. |
|
|
575 |
|
|
|
576 |
|
|
|
577 |
- |
|
|
578 |
|
|
|
579 |
|
|
|
580 |
__yyterminate()__ can be used in lieu of a return |
|
|
581 |
statement in an action. It terminates the scanner and |
|
|
582 |
returns a 0 to the scanner's caller, indicating |
|
|
583 |
__yyterminate()__ is also called |
|
|
584 |
when an end-of-file is encountered. It is a macro and may be |
|
|
585 |
redefined. |
|
|
586 |
!!THE GENERATED SCANNER |
|
|
587 |
|
|
|
588 |
|
|
|
589 |
The output of ''flex'' is the file __lex.yy.c,__ which |
|
|
590 |
contains the scanning routine __yylex(),__ a number of |
|
|
591 |
tables used by it for matching tokens, and a number of |
|
|
592 |
auxiliary routines and macros. By default, __yylex()__ is |
|
|
593 |
declared as follows: |
|
|
594 |
|
|
|
595 |
|
|
|
596 |
int yylex() |
|
|
597 |
{ |
|
|
598 |
... various definitions and the actions in here ... |
|
|
599 |
} |
|
|
600 |
(If your environment supports function prototypes, then it will be |
|
|
601 |
|
|
|
602 |
|
|
|
603 |
#define YY_DECL float lexscan( a, b ) float a, b; |
|
|
604 |
to give the scanning routine the name ''lexscan,'' returning a float, and taking two floats as arguments. Note that if you give arguments to the scanning routine using a K'' |
|
|
605 |
|
|
|
606 |
|
|
|
607 |
Whenever __yylex()__ is called, it scans tokens from the |
|
|
608 |
global input file ''yyin'' (which defaults to stdin). It |
|
|
609 |
continues until it either reaches an end-of-file (at which |
|
|
610 |
point it returns the value 0) or one of its actions executes |
|
|
611 |
a ''return'' statement. |
|
|
612 |
|
|
|
613 |
|
|
|
614 |
If the scanner reaches an end-of-file, subsequent calls are |
|
|
615 |
undefined unless either ''yyin'' is pointed at a new |
|
|
616 |
input file (in which case scanning continues from that |
|
|
617 |
file), or __yyrestart()__ is called. __yyrestart()__ |
|
|
618 |
takes one argument, a __FILE *__ pointer (which can be |
|
|
619 |
nil, if you've set up __YY_INPUT__ to scan from a source |
|
|
620 |
other than ''yyin),'' and initializes ''yyin'' for |
|
|
621 |
scanning from that file. Essentially there is no difference |
|
|
622 |
between just assigning ''yyin'' to a new input file or |
|
|
623 |
using __yyrestart()__ to do so; the latter is available |
|
|
624 |
for compatibility with previous versions of ''flex,'' and |
|
|
625 |
because it can be used to switch input files in the middle |
|
|
626 |
of scanning. It can also be used to throw away the current |
|
|
627 |
input buffer, by calling it with an argument of ''yyin;'' |
|
|
628 |
but better is to use __YY_FLUSH_BUFFER__ (see above). |
|
|
629 |
Note that __yyrestart()__ does ''not'' reset the start |
|
|
630 |
condition to __INITIAL__ (see Start Conditions, |
|
|
631 |
below). |
|
|
632 |
|
|
|
633 |
|
|
|
634 |
If __yylex()__ stops scanning due to executing a |
|
|
635 |
''return'' statement in one of the actions, the scanner |
|
|
636 |
may then be called again and it will resume scanning where |
|
|
637 |
it left off. |
|
|
638 |
|
|
|
639 |
|
|
|
640 |
By default (and for purposes of efficiency), the scanner |
|
|
641 |
uses block-reads rather than simple ''getc()'' calls to |
|
|
642 |
read characters from ''yyin.'' The nature of how it gets |
|
|
643 |
its input can be controlled by defining the __YY_INPUT__ |
|
|
644 |
macro. YY_INPUT's calling sequence is |
|
|
645 |
__max_size'' characters in the character |
|
|
646 |
array ''buf'' and return in the integer variable |
|
|
647 |
''result'' either the number of characters read or the |
|
|
648 |
constant YY_NULL (0 on Unix systems) to indicate EOF. The |
|
|
649 |
default YY_INPUT reads from the global file-pointer |
|
|
650 |
'' |
|
|
651 |
|
|
|
652 |
|
|
|
653 |
A sample definition of YY_INPUT (in the definitions section |
|
|
654 |
of the input file): |
|
|
655 |
|
|
|
656 |
|
|
|
657 |
%{ |
|
|
658 |
#define YY_INPUT(buf,result,max_size) \ |
|
|
659 |
{ \ |
|
|
660 |
int c = getchar(); \ |
|
|
661 |
result = (c == EOF) ? YY_NULL : (buf[[0] = c, 1); \ |
|
|
662 |
} |
|
|
663 |
%} |
|
|
664 |
This definition will change the input processing to occur one character at a time. |
|
|
665 |
|
|
|
666 |
|
|
|
667 |
When the scanner receives an end-of-file indication from |
|
|
668 |
YY_INPUT, it then checks the __yywrap()__ function. If |
|
|
669 |
__yywrap()__ returns false (zero), then it is assumed |
|
|
670 |
that the function has gone ahead and set up ''yyin'' to |
|
|
671 |
point to another input file, and scanning continues. If it |
|
|
672 |
returns true (non-zero), then the scanner terminates, |
|
|
673 |
returning 0 to its caller. Note that in either case, the |
|
|
674 |
start condition remains unchanged; it does ''not'' revert |
|
|
675 |
to __INITIAL.__ |
|
|
676 |
|
|
|
677 |
|
|
|
678 |
If you do not supply your own version of __yywrap(),__ |
|
|
679 |
then you must either use __%option noyywrap__ (in which |
|
|
680 |
case the scanner behaves as though __yywrap()__ returned |
|
|
681 |
1), or you must link with __-lfl__ to obtain the default |
|
|
682 |
version of the routine, which always returns 1. |
|
|
683 |
|
|
|
684 |
|
|
|
685 |
Three routines are available for scanning from in-memory |
|
|
686 |
buffers rather than files: __yy_scan_string(), |
|
|
687 |
yy_scan_bytes(),__ and __yy_scan_buffer().__ See the |
|
|
688 |
discussion of them below in the section Multiple Input |
|
|
689 |
Buffers. |
|
|
690 |
|
|
|
691 |
|
|
|
692 |
The scanner writes its __ECHO__ output to the |
|
|
693 |
''yyout'' global (default, stdout), which may be |
|
|
694 |
redefined by the user simply by assigning it to some other |
|
|
695 |
__FILE__ pointer. |
|
|
696 |
!!START CONDITIONS |
|
|
697 |
|
|
|
698 |
|
|
|
699 |
''flex'' provides a mechanism for conditionally |
|
|
700 |
activating rules. Any rule whose pattern is prefixed with |
|
|
701 |
'' |
|
|
702 |
|
|
|
703 |
|
|
|
704 |
will be active only when the scanner is in the |
|
|
705 |
|
|
|
706 |
|
|
|
707 |
will be active only when the current start condition is either |
|
|
708 |
|
|
|
709 |
|
|
|
710 |
Start conditions are declared in the definitions (first) |
|
|
711 |
section of the input using unindented lines beginning with |
|
|
712 |
either __%s__ or __%x__ followed by a list of names. |
|
|
713 |
The former declares ''inclusive'' start conditions, the |
|
|
714 |
latter ''exclusive'' start conditions. A start condition |
|
|
715 |
is activated using the __BEGIN__ action. Until the next |
|
|
716 |
__BEGIN__ action is executed, rules with the given start |
|
|
717 |
condition will be active and rules with other start |
|
|
718 |
conditions will be inactive. If the start condition is |
|
|
719 |
''inclusive,'' then rules with no start conditions at all |
|
|
720 |
will also be active. If it is ''exclusive,'' then |
|
|
721 |
''only'' rules qualified with the start condition will be |
|
|
722 |
active. A set of rules contingent on the same exclusive |
|
|
723 |
start condition describe a scanner which is independent of |
|
|
724 |
any of the other rules in the ''flex'' input. Because of |
|
|
725 |
this, exclusive start conditions make it easy to specify |
|
|
726 |
'' |
|
|
727 |
|
|
|
728 |
|
|
|
729 |
If the distinction between inclusive and exclusive start |
|
|
730 |
conditions is still a little vague, here's a simple example |
|
|
731 |
illustrating the connection between the two. The set of |
|
|
732 |
rules: |
|
|
733 |
|
|
|
734 |
|
|
|
735 |
%s example |
|
|
736 |
%% |
|
|
737 |
is equivalent to |
|
|
738 |
|
|
|
739 |
|
|
|
740 |
%x example |
|
|
741 |
%% |
|
|
742 |
Without the ____ qualifier, the ''bar'' pattern in the second example wouldn't be active (i.e., couldn't match) when in start condition __example.__ If we just used ____ to qualify ''bar,'' though, then it would only be active in __example__ and not in __INITIAL,__ while in the first example it's active in both, because in the first example the __example__ startion condition is an ''inclusive'' __(%s)__ start condition. |
|
|
743 |
|
|
|
744 |
|
|
|
745 |
Also note that the special start-condition specifier |
|
|
746 |
____ matches every start condition. Thus, the |
|
|
747 |
above example could also have been written; |
|
|
748 |
|
|
|
749 |
|
|
|
750 |
%x example |
|
|
751 |
%% |
|
|
752 |
The default rule (to __ECHO__ any unmatched character) remains active in start conditions. It is equivalent to: |
|
|
753 |
|
|
|
754 |
|
|
|
755 |
__BEGIN(0)__ returns to the original state where only the rules with no start conditions are active. This state can also be referred to as the start-condition __BEGIN(INITIAL)__ is equivalent to __BEGIN(0).__ (The parentheses around the start condition name are not required but are considered good style.) |
|
|
756 |
|
|
|
757 |
|
|
|
758 |
__BEGIN__ actions can also be given as indented code at |
|
|
759 |
the beginning of the rules section. For example, the |
|
|
760 |
following will cause the scanner to enter the |
|
|
761 |
__yylex()__ |
|
|
762 |
is called and the global variable ''enter_special'' is |
|
|
763 |
true: |
|
|
764 |
|
|
|
765 |
|
|
|
766 |
int enter_special; |
|
|
767 |
%x SPECIAL |
|
|
768 |
%% |
|
|
769 |
if ( enter_special ) |
|
|
770 |
BEGIN(SPECIAL); |
|
|
771 |
To illustrate the uses of start conditions, here is a scanner which provides two different interpretations of a string like |
|
|
772 |
|
|
|
773 |
|
|
|
774 |
%{ |
|
|
775 |
#include |
|
|
776 |
Here is a scanner which recognizes (and discards) C comments while maintaining a count of the current input line. |
|
|
777 |
|
|
|
778 |
|
|
|
779 |
%x comment |
|
|
780 |
%% |
|
|
781 |
int line_num = 1; |
|
|
782 |
This scanner goes to a bit of trouble to match as much text as possible with each rule. In general, when attempting to write a high-speed scanner try to match as much possible in each rule, as it's a big win. |
|
|
783 |
|
|
|
784 |
|
|
|
785 |
Note that start-conditions names are really integer values |
|
|
786 |
and can be stored as such. Thus, the above could be extended |
|
|
787 |
in the following fashion: |
|
|
788 |
|
|
|
789 |
|
|
|
790 |
%x comment foo |
|
|
791 |
%% |
|
|
792 |
int line_num = 1; |
|
|
793 |
int comment_caller; |
|
|
794 |
Furthermore, you can access the current start condition using the integer-valued __YY_START__ macro. For example, the above assignments to ''comment_caller'' could instead be written |
|
|
795 |
|
|
|
796 |
|
|
|
797 |
comment_caller = YY_START; |
|
|
798 |
Flex provides __YYSTATE__ as an alias for __YY_START__ (since that is what's used by AT__lex).'' |
|
|
799 |
|
|
|
800 |
|
|
|
801 |
Note that start conditions do not have their own name-space; |
|
|
802 |
%s's and %x's declare names in the same fashion as |
|
|
803 |
#define's. |
|
|
804 |
|
|
|
805 |
|
|
|
806 |
Finally, here's an example of how to match C-style quoted |
|
|
807 |
strings using exclusive start conditions, including expanded |
|
|
808 |
escape sequences (but not including checking for a string |
|
|
809 |
that's too long): |
|
|
810 |
|
|
|
811 |
|
|
|
812 |
%x str |
|
|
813 |
%% |
|
|
814 |
char string_buf[[MAX_STR_CONST]; |
|
|
815 |
char *string_buf_ptr; |
|
|
816 |
Often, such as in some of the examples above, you wind up writing a whole bunch of rules all preceded by the same start condition(s). Flex makes this a little easier and cleaner by introducing a notion of start condition ''scope.'' A start condition scope is begun with: |
|
|
817 |
|
|
|
818 |
|
|
|
819 |
where ''SCs'' is a list of one or more start conditions. Inside the start condition scope, every rule automatically has the prefix '''' applied to it, until a '''}''' which matches the initial '''{'.'' So, for example, |
|
|
820 |
|
|
|
821 |
|
|
|
822 |
is equivalent to: |
|
|
823 |
|
|
|
824 |
|
|
|
825 |
Start condition scopes may be nested. |
|
|
826 |
|
|
|
827 |
|
|
|
828 |
Three routines are available for manipulating stacks of |
|
|
829 |
start conditions: |
|
|
830 |
|
|
|
831 |
|
|
|
832 |
__void yy_push_state(int new_state)__ |
|
|
833 |
|
|
|
834 |
|
|
|
835 |
pushes the current start condition onto the top of the start |
|
|
836 |
condition stack and switches to ''new_state'' as though |
|
|
837 |
you had used __BEGIN new_state__ (recall that start |
|
|
838 |
condition names are also integers). |
|
|
839 |
|
|
|
840 |
|
|
|
841 |
__void yy_pop_state()__ |
|
|
842 |
|
|
|
843 |
|
|
|
844 |
pops the top of the stack and switches to it via |
|
|
845 |
__BEGIN.__ |
|
|
846 |
|
|
|
847 |
|
|
|
848 |
__int yy_top_state()__ |
|
|
849 |
|
|
|
850 |
|
|
|
851 |
returns the top of the stack without altering the stack's |
|
|
852 |
contents. |
|
|
853 |
|
|
|
854 |
|
|
|
855 |
The start condition stack grows dynamically and so has no |
|
|
856 |
built-in size limitation. If memory is exhausted, program |
|
|
857 |
execution aborts. |
|
|
858 |
|
|
|
859 |
|
|
|
860 |
To use start condition stacks, your scanner must include a |
|
|
861 |
__%option stack__ directive (see Options |
|
|
862 |
below). |
|
|
863 |
!!MULTIPLE INPUT BUFFERS |
|
|
864 |
|
|
|
865 |
|
|
|
866 |
Some scanners (such as those which support |
|
|
867 |
flex'' scanners do a large amount of |
|
|
868 |
buffering, one cannot control where the next input will be |
|
|
869 |
read from by simply writing a __YY_INPUT__ which is |
|
|
870 |
sensitive to the scanning context. __YY_INPUT__ is only |
|
|
871 |
called when the scanner reaches the end of its buffer, which |
|
|
872 |
may be a long time after scanning a statement such as an |
|
|
873 |
__ |
|
|
874 |
|
|
|
875 |
|
|
|
876 |
To negotiate these sorts of problems, ''flex'' provides a |
|
|
877 |
mechanism for creating and switching between multiple input |
|
|
878 |
buffers. An input buffer is created by using: |
|
|
879 |
|
|
|
880 |
|
|
|
881 |
YY_BUFFER_STATE yy_create_buffer( FILE *file, int size ) |
|
|
882 |
which takes a ''FILE'' pointer and a size and creates a buffer associated with the given file and large enough to hold ''size'' characters (when in doubt, use __YY_BUF_SIZE__ for the size). It returns a __YY_BUFFER_STATE__ handle, which may then be passed to other routines (see below). The __YY_BUFFER_STATE__ type is a pointer to an opaque __struct yy_buffer_state__ structure, so you may safely initialize YY_BUFFER_STATE variables to __((YY_BUFFER_STATE) 0)__ if you wish, and also refer to the opaque structure in order to correctly declare input buffers in source files other than that of your scanner. Note that the ''FILE'' pointer in the call to __yy_create_buffer__ is only used as the value of ''yyin'' seen by __YY_INPUT;__ if you redefine __YY_INPUT__ so it no longer uses ''yyin,'' then you can safely pass a nil ''FILE'' pointer to __yy_create_buffer.__ You select a particular buffer to scan from using: |
|
|
883 |
|
|
|
884 |
|
|
|
885 |
void yy_switch_to_buffer( YY_BUFFER_STATE new_buffer ) |
|
|
886 |
switches the scanner's input buffer so subsequent tokens will come from ''new_buffer.'' Note that __yy_switch_to_buffer()__ may be used by yywrap() to set things up for continued scanning, instead of opening a new file and pointing ''yyin'' at it. Note also that switching input sources via either __yy_switch_to_buffer()__ or __yywrap()__ does ''not'' change the start condition. |
|
|
887 |
|
|
|
888 |
|
|
|
889 |
void yy_delete_buffer( YY_BUFFER_STATE buffer ) |
|
|
890 |
is used to reclaim the storage associated with a buffer. ( __buffer__ can be nil, in which case the routine does nothing.) You can also clear the current contents of a buffer using: |
|
|
891 |
|
|
|
892 |
|
|
|
893 |
void yy_flush_buffer( YY_BUFFER_STATE buffer ) |
|
|
894 |
This function discards the buffer's contents, so the next time the scanner attempts to match a token from the buffer, it will first fill the buffer anew using __YY_INPUT.__ |
|
|
895 |
|
|
|
896 |
|
|
|
897 |
__yy_new_buffer()__ is an alias for |
|
|
898 |
__yy_create_buffer(),__ provided for compatibility with |
|
|
899 |
the C++ use of ''new'' and ''delete'' for creating and |
|
|
900 |
destroying dynamic objects. |
|
|
901 |
|
|
|
902 |
|
|
|
903 |
Finally, the __YY_CURRENT_BUFFER__ macro returns a |
|
|
904 |
__YY_BUFFER_STATE__ handle to the current |
|
|
905 |
buffer. |
|
|
906 |
|
|
|
907 |
|
|
|
908 |
Here is an example of using these features for writing a |
|
|
909 |
scanner which expands include files (the |
|
|
910 |
____ feature is discussed |
|
|
911 |
below): |
|
|
912 |
|
|
|
913 |
|
|
|
914 |
/* the |
|
|
915 |
Three routines are available for setting up input buffers for scanning in-memory strings instead of files. All of them create a new input buffer for scanning the string, and return a corresponding __YY_BUFFER_STATE__ handle (which you should delete with __yy_delete_buffer()__ when done with it). They also switch to the new buffer using __yy_switch_to_buffer(),__ so the next call to __yylex()__ will start scanning the string. |
|
|
916 |
|
|
|
917 |
|
|
|
918 |
__yy_scan_string(const char *str)__ |
|
|
919 |
|
|
|
920 |
|
|
|
921 |
scans a NUL-terminated string. |
|
|
922 |
|
|
|
923 |
|
|
|
924 |
__yy_scan_bytes(const char *bytes, int |
|
|
925 |
len)__ |
|
|
926 |
|
|
|
927 |
|
|
|
928 |
scans ''len'' bytes (including possibly NUL's) starting |
|
|
929 |
at location ''bytes.'' |
|
|
930 |
|
|
|
931 |
|
|
|
932 |
Note that both of these functions create and scan a |
|
|
933 |
''copy'' of the string or bytes. (This may be desirable, |
|
|
934 |
since __yylex()__ modifies the contents of the buffer it |
|
|
935 |
is scanning.) You can avoid the copy by using: |
|
|
936 |
|
|
|
937 |
|
|
|
938 |
__yy_scan_buffer(char *base, yy_size_t |
|
|
939 |
size)__ |
|
|
940 |
|
|
|
941 |
|
|
|
942 |
which scans in place the buffer starting at ''base,'' |
|
|
943 |
consisting of ''size'' bytes, the last two bytes of which |
|
|
944 |
''must'' be __YY_END_OF_BUFFER_CHAR__ (ASCII NUL). |
|
|
945 |
These last two bytes are not scanned; thus, scanning |
|
|
946 |
consists of __base[[0]__ through __base[[size-2],__ |
|
|
947 |
inclusive. |
|
|
948 |
|
|
|
949 |
|
|
|
950 |
If you fail to set up ''base'' in this manner (i.e., |
|
|
951 |
forget the final two __YY_END_OF_BUFFER_CHAR__ bytes), |
|
|
952 |
then __yy_scan_buffer()__ returns a nil pointer instead |
|
|
953 |
of creating a new input buffer. |
|
|
954 |
|
|
|
955 |
|
|
|
956 |
The type __yy_size_t__ is an integral type to which you |
|
|
957 |
can cast an integer expression reflecting the size of the |
|
|
958 |
buffer. |
|
|
959 |
!!END-OF-FILE RULES |
|
|
960 |
|
|
|
961 |
|
|
|
962 |
The special rule |
|
|
963 |
|
|
|
964 |
|
|
|
965 |
- |
|
|
966 |
|
|
|
967 |
|
|
|
968 |
assigning ''yyin'' to a new input file (in previous |
|
|
969 |
versions of flex, after doing the assignment you had to call |
|
|
970 |
the special action __YY_NEW_FILE;__ this is no longer |
|
|
971 |
necessary); |
|
|
972 |
|
|
|
973 |
|
|
|
974 |
- |
|
|
975 |
|
|
|
976 |
|
|
|
977 |
executing a ''return'' statement; |
|
|
978 |
|
|
|
979 |
|
|
|
980 |
- |
|
|
981 |
|
|
|
982 |
|
|
|
983 |
executing the special __yyterminate()__ |
|
|
984 |
action; |
|
|
985 |
|
|
|
986 |
|
|
|
987 |
- |
|
|
988 |
|
|
|
989 |
|
|
|
990 |
or, switching to a new buffer using |
|
|
991 |
__yy_switch_to_buffer()__ as shown in the example |
|
|
992 |
above. |
|
|
993 |
|
|
|
994 |
|
|
|
995 |
all'' start conditions which do |
|
|
996 |
not already have |
|
|
997 |
'' |
|
|
998 |
|
|
|
999 |
|
|
|
1000 |
These rules are useful for catching things like unclosed comments. An example: |
|
|
1001 |
|
|
|
1002 |
|
|
|
1003 |
%x quote |
|
|
1004 |
%% |
|
|
1005 |
...other rules for dealing with quotes... |
|
|
1006 |
!!MISCELLANEOUS MACROS |
|
|
1007 |
|
|
|
1008 |
|
|
|
1009 |
The macro __YY_USER_ACTION__ can be defined to provide an |
|
|
1010 |
action which is always executed prior to the matched rule's |
|
|
1011 |
action. For example, it could be #define'd to call a routine |
|
|
1012 |
to convert yytext to lower-case. When __YY_USER_ACTION__ |
|
|
1013 |
is invoked, the variable ''yy_act'' gives the number of |
|
|
1014 |
the matched rule (rules are numbered starting with 1). |
|
|
1015 |
Suppose you want to profile how often each of your rules is |
|
|
1016 |
matched. The following would do the trick: |
|
|
1017 |
|
|
|
1018 |
|
|
|
1019 |
#define YY_USER_ACTION ++ctr[[yy_act] |
|
|
1020 |
where ''ctr'' is an array to hold the counts for the different rules. Note that the macro __YY_NUM_RULES__ gives the total number of rules (including the default rule, even if you use __-s),__ so a correct declaration for ''ctr'' is: |
|
|
1021 |
|
|
|
1022 |
|
|
|
1023 |
int ctr[[YY_NUM_RULES]; |
|
|
1024 |
The macro __YY_USER_INIT__ may be defined to provide an action which is always executed before the first scan (and before the scanner's internal initializations are done). For example, it could be used to call a routine to read in a data table or open a logging file. |
|
|
1025 |
|
|
|
1026 |
|
|
|
1027 |
The macro __yy_set_interactive(is_interactive)__ can be |
|
|
1028 |
used to control whether the current buffer is considered |
|
|
1029 |
''interactive.'' An interactive buffer is processed more |
|
|
1030 |
slowly, but must be used when the scanner's input source is |
|
|
1031 |
indeed interactive to avoid problems due to waiting to fill |
|
|
1032 |
buffers (see the discussion of the __-I__ flag below). A |
|
|
1033 |
non-zero value in the macro invocation marks the buffer as |
|
|
1034 |
interactive, a zero value as non-interactive. Note that use |
|
|
1035 |
of this macro overrides __%option always-interactive__ or |
|
|
1036 |
__%option never-interactive__ (see Options below). |
|
|
1037 |
__yy_set_interactive()__ must be invoked prior to |
|
|
1038 |
beginning to scan the buffer that is (or is not) to be |
|
|
1039 |
considered interactive. |
|
|
1040 |
|
|
|
1041 |
|
|
|
1042 |
The macro __yy_set_bol(at_bol)__ can be used to control |
|
|
1043 |
whether the current buffer's scanning context for the next |
|
|
1044 |
token match is done as though at the beginning of a line. A |
|
|
1045 |
non-zero macro argument makes rules anchored with '^' |
|
|
1046 |
active, while a zero argument makes '^' rules |
|
|
1047 |
inactive. |
|
|
1048 |
|
|
|
1049 |
|
|
|
1050 |
The macro __YY_AT_BOL()__ returns true if the next token |
|
|
1051 |
scanned from the current buffer will have '^' rules active, |
|
|
1052 |
false otherwise. |
|
|
1053 |
|
|
|
1054 |
|
|
|
1055 |
In the generated scanner, the actions are all gathered in |
|
|
1056 |
one large switch statement and separated using |
|
|
1057 |
__YY_BREAK,__ which may be redefined. By default, it is |
|
|
1058 |
simply a |
|
|
1059 |
__YY_BREAK__ |
|
|
1060 |
allows, for example, C++ users to #define YY_BREAK to do |
|
|
1061 |
nothing (while being very careful that every rule ends with |
|
|
1062 |
a |
|
|
1063 |
__YY_BREAK__ is inaccessible. |
|
|
1064 |
!!VALUES AVAILABLE TO THE USER |
|
|
1065 |
|
|
|
1066 |
|
|
|
1067 |
This section summarizes the various values available to the |
|
|
1068 |
user in the rule actions. |
|
|
1069 |
|
|
|
1070 |
|
|
|
1071 |
- |
|
|
1072 |
|
|
|
1073 |
|
|
|
1074 |
__char *yytext__ holds the text of the current token. It |
|
|
1075 |
may be modified but not lengthened (you cannot append |
|
|
1076 |
characters to the end). |
|
|
1077 |
|
|
|
1078 |
|
|
|
1079 |
If the special directive __%array__ appears in the first |
|
|
1080 |
section of the scanner description, then __yytext__ is |
|
|
1081 |
instead declared __char yytext[[YYLMAX],__ where |
|
|
1082 |
__YYLMAX__ is a macro definition that you can redefine in |
|
|
1083 |
the first section if you don't like the default value |
|
|
1084 |
(generally 8KB). Using __%array__ results in somewhat |
|
|
1085 |
slower scanners, but the value of __yytext__ becomes |
|
|
1086 |
immune to calls to ''input()'' and ''unput(),'' which |
|
|
1087 |
potentially destroy its value when __yytext__ is a |
|
|
1088 |
character pointer. The opposite of __%array__ is |
|
|
1089 |
__%pointer,__ which is the default. |
|
|
1090 |
|
|
|
1091 |
|
|
|
1092 |
You cannot use __%array__ when generating C++ scanner |
|
|
1093 |
classes (the __-+__ flag). |
|
|
1094 |
|
|
|
1095 |
|
|
|
1096 |
- |
|
|
1097 |
|
|
|
1098 |
|
|
|
1099 |
__int yyleng__ holds the length of the current |
|
|
1100 |
token. |
|
|
1101 |
|
|
|
1102 |
|
|
|
1103 |
- |
|
|
1104 |
|
|
|
1105 |
|
|
|
1106 |
__FILE *yyin__ is the file which by default ''flex'' |
|
|
1107 |
reads from. It may be redefined but doing so only makes |
|
|
1108 |
sense before scanning begins or after an EOF has been |
|
|
1109 |
encountered. Changing it in the midst of scanning will have |
|
|
1110 |
unexpected results since ''flex'' buffers its input; use |
|
|
1111 |
__yyrestart()__ instead. Once scanning terminates because |
|
|
1112 |
an end-of-file has been seen, you can assign ''yyin'' at |
|
|
1113 |
the new input file and then call the scanner again to |
|
|
1114 |
continue scanning. |
|
|
1115 |
|
|
|
1116 |
|
|
|
1117 |
- |
|
|
1118 |
|
|
|
1119 |
|
|
|
1120 |
__void yyrestart( FILE *new_file )__ may be called to |
|
|
1121 |
point ''yyin'' at the new input file. The switch-over to |
|
|
1122 |
the new file is immediate (any previously buffered-up input |
|
|
1123 |
is lost). Note that calling __yyrestart()__ with |
|
|
1124 |
''yyin'' as an argument thus throws away the current |
|
|
1125 |
input buffer and continues scanning the same input |
|
|
1126 |
file. |
|
|
1127 |
|
|
|
1128 |
|
|
|
1129 |
- |
|
|
1130 |
|
|
|
1131 |
|
|
|
1132 |
__FILE *yyout__ is the file to which __ECHO__ actions |
|
|
1133 |
are done. It can be reassigned by the user. |
|
|
1134 |
|
|
|
1135 |
|
|
|
1136 |
- |
|
|
1137 |
|
|
|
1138 |
|
|
|
1139 |
__YY_CURRENT_BUFFER__ returns a __YY_BUFFER_STATE__ |
|
|
1140 |
handle to the current buffer. |
|
|
1141 |
|
|
|
1142 |
|
|
|
1143 |
- |
|
|
1144 |
|
|
|
1145 |
|
|
|
1146 |
__YY_START__ returns an integer value corresponding to |
|
|
1147 |
the current start condition. You can subsequently use this |
|
|
1148 |
value with __BEGIN__ to return to that start |
|
|
1149 |
condition. |
|
|
1150 |
!!INTERFACING WITH YACC |
|
|
1151 |
|
|
|
1152 |
|
|
|
1153 |
One of the main uses of ''flex'' is as a companion to the |
|
|
1154 |
''yacc'' parser-generator. ''yacc'' parsers expect to |
|
|
1155 |
call a routine named __yylex()__ to find the next input |
|
|
1156 |
token. The routine is supposed to return the type of the |
|
|
1157 |
next token as well as putting any associated value in the |
|
|
1158 |
global __yylval.__ To use ''flex'' with ''yacc,'' |
|
|
1159 |
one specifies the __-d__ option to ''yacc'' to |
|
|
1160 |
instruct it to generate the file __y.tab.h__ containing |
|
|
1161 |
definitions of all the __%tokens__ appearing in the |
|
|
1162 |
''yacc'' input. This file is then included in the |
|
|
1163 |
''flex'' scanner. For example, if one of the tokens is |
|
|
1164 |
'' |
|
|
1165 |
|
|
|
1166 |
|
|
|
1167 |
%{ |
|
|
1168 |
#include |
|
|
1169 |
!!OPTIONS |
|
|
1170 |
|
|
|
1171 |
|
|
|
1172 |
''flex'' has the following options: |
|
|
1173 |
|
|
|
1174 |
|
|
|
1175 |
__-b__ |
|
|
1176 |
|
|
|
1177 |
|
|
|
1178 |
Generate backing-up information to ''lex.backup.'' This |
|
|
1179 |
is a list of scanner states which require backing up and the |
|
|
1180 |
input characters on which they do so. By adding rules one |
|
|
1181 |
can remove backing-up states. If ''all'' backing-up |
|
|
1182 |
states are eliminated and __-Cf__ or __-CF__ is used, |
|
|
1183 |
the generated scanner will run faster (see the __-p__ |
|
|
1184 |
flag). Only users who wish to squeeze every last cycle out |
|
|
1185 |
of their scanners need worry about this option. (See the |
|
|
1186 |
section on Performance Considerations below.) |
|
|
1187 |
|
|
|
1188 |
|
|
|
1189 |
__-c__ |
|
|
1190 |
|
|
|
1191 |
|
|
|
1192 |
is a do-nothing, deprecated option included for POSIX |
|
|
1193 |
compliance. |
|
|
1194 |
|
|
|
1195 |
|
|
|
1196 |
__-d__ |
|
|
1197 |
|
|
|
1198 |
|
|
|
1199 |
makes the generated scanner run in ''debug'' mode. |
|
|
1200 |
Whenever a pattern is recognized and the global |
|
|
1201 |
__yy_flex_debug__ is non-zero (which is the default), the |
|
|
1202 |
scanner will write to ''stderr'' a line of the |
|
|
1203 |
form: |
|
|
1204 |
|
|
|
1205 |
|
|
|
1206 |
--accepting rule at line 53 ( |
|
|
1207 |
The line number refers to the location of the rule in the file defining the scanner (i.e., the file that was fed to flex). Messages are also generated when the scanner backs up, accepts the default rule, reaches the end of its input buffer (or encounters a NUL; at this point, the two look the same as far as the scanner's concerned), or reaches an end-of-file. |
|
|
1208 |
|
|
|
1209 |
|
|
|
1210 |
__-f__ |
|
|
1211 |
|
|
|
1212 |
|
|
|
1213 |
specifies ''fast scanner.'' No table compression is done |
|
|
1214 |
and stdio is bypassed. The result is large but fast. This |
|
|
1215 |
option is equivalent to __-Cfr__ (see |
|
|
1216 |
below). |
|
|
1217 |
|
|
|
1218 |
|
|
|
1219 |
__-h__ |
|
|
1220 |
|
|
|
1221 |
|
|
|
1222 |
generates a flex's'' |
|
|
1223 |
options to ''stdout'' and then exits. __-?__ and |
|
|
1224 |
__--help__ are synonyms for __-h.__ |
|
|
1225 |
|
|
|
1226 |
|
|
|
1227 |
__-i__ |
|
|
1228 |
|
|
|
1229 |
|
|
|
1230 |
instructs ''flex'' to generate a ''case-insensitive'' |
|
|
1231 |
scanner. The case of letters given in the ''flex'' input |
|
|
1232 |
patterns will be ignored, and tokens in the input will be |
|
|
1233 |
matched regardless of case. The matched text given in |
|
|
1234 |
''yytext'' will have the preserved case (i.e., it will |
|
|
1235 |
not be folded). |
|
|
1236 |
|
|
|
1237 |
|
|
|
1238 |
__-l__ |
|
|
1239 |
|
|
|
1240 |
|
|
|
1241 |
turns on maximum compatibility with the original AT |
|
|
1242 |
lex'' implementation. Note that this does not mean |
|
|
1243 |
''full'' compatibility. Use of this option costs a |
|
|
1244 |
considerable amount of performance, and it cannot be used |
|
|
1245 |
with the __-+, -f, -F, -Cf,__ or __-CF__ options. For |
|
|
1246 |
details on the compatibilities it provides, see the section |
|
|
1247 |
__YY_FLEX_LEX_COMPAT__ |
|
|
1248 |
being #define'd in the generated scanner. |
|
|
1249 |
|
|
|
1250 |
|
|
|
1251 |
__-n__ |
|
|
1252 |
|
|
|
1253 |
|
|
|
1254 |
is another do-nothing, deprecated option included only for |
|
|
1255 |
POSIX compliance. |
|
|
1256 |
|
|
|
1257 |
|
|
|
1258 |
__-p__ |
|
|
1259 |
|
|
|
1260 |
|
|
|
1261 |
generates a performance report to stderr. The report |
|
|
1262 |
consists of comments regarding features of the ''flex'' |
|
|
1263 |
input file which will cause a serious loss of performance in |
|
|
1264 |
the resulting scanner. If you give the flag twice, you will |
|
|
1265 |
also get comments regarding features that lead to minor |
|
|
1266 |
performance losses. |
|
|
1267 |
|
|
|
1268 |
|
|
|
1269 |
Note that the use of __REJECT, %option yylineno,__ and |
|
|
1270 |
variable trailing context (see the Deficiencies / Bugs |
|
|
1271 |
section below) entails a substantial performance penalty; |
|
|
1272 |
use of ''yymore(),'' the __^__ operator, and the |
|
|
1273 |
__-I__ flag entail minor performance |
|
|
1274 |
penalties. |
|
|
1275 |
|
|
|
1276 |
|
|
|
1277 |
__-s__ |
|
|
1278 |
|
|
|
1279 |
|
|
|
1280 |
causes the ''default rule'' (that unmatched scanner input |
|
|
1281 |
is echoed to ''stdout)'' to be suppressed. If the scanner |
|
|
1282 |
encounters input that does not match any of its rules, it |
|
|
1283 |
aborts with an error. This option is useful for finding |
|
|
1284 |
holes in a scanner's rule set. |
|
|
1285 |
|
|
|
1286 |
|
|
|
1287 |
__-t__ |
|
|
1288 |
|
|
|
1289 |
|
|
|
1290 |
instructs ''flex'' to write the scanner it generates to |
|
|
1291 |
standard output instead of __lex.yy.c.__ |
|
|
1292 |
|
|
|
1293 |
|
|
|
1294 |
__-v__ |
|
|
1295 |
|
|
|
1296 |
|
|
|
1297 |
specifies that ''flex'' should write to ''stderr'' a |
|
|
1298 |
summary of statistics regarding the scanner it generates. |
|
|
1299 |
Most of the statistics are meaningless to the casual |
|
|
1300 |
''flex'' user, but the first line identifies the version |
|
|
1301 |
of ''flex'' (same as reported by __-V),__ and the next |
|
|
1302 |
line the flags used when generating the scanner, including |
|
|
1303 |
those that are on by default. |
|
|
1304 |
|
|
|
1305 |
|
|
|
1306 |
__-w__ |
|
|
1307 |
|
|
|
1308 |
|
|
|
1309 |
suppresses warning messages. |
|
|
1310 |
|
|
|
1311 |
|
|
|
1312 |
__-B__ |
|
|
1313 |
|
|
|
1314 |
|
|
|
1315 |
instructs ''flex'' to generate a ''batch'' scanner, |
|
|
1316 |
the opposite of ''interactive'' scanners generated by |
|
|
1317 |
__-I__ (see below). In general, you use __-B__ when |
|
|
1318 |
you are ''certain'' that your scanner will never be used |
|
|
1319 |
interactively, and you want to squeeze a ''little'' more |
|
|
1320 |
performance out of it. If your goal is instead to squeeze |
|
|
1321 |
out a ''lot'' more performance, you should be using the |
|
|
1322 |
__-Cf__ or __-CF__ options (discussed below), which |
|
|
1323 |
turn on __-B__ automatically anyway. |
|
|
1324 |
|
|
|
1325 |
|
|
|
1326 |
__-F__ |
|
|
1327 |
|
|
|
1328 |
|
|
|
1329 |
specifies that the ''fast'' scanner table representation |
|
|
1330 |
should be used (and stdio bypassed). This representation is |
|
|
1331 |
about as fast as the full table representation __(-f),__ |
|
|
1332 |
and for some sets of patterns will be considerably smaller |
|
|
1333 |
(and for others, larger). In general, if the pattern set |
|
|
1334 |
contains both |
|
|
1335 |
__ |
|
|
1336 |
|
|
|
1337 |
|
|
|
1338 |
then you're better off using the full table representation. If only the -F.__ |
|
|
1339 |
|
|
|
1340 |
|
|
|
1341 |
This option is equivalent to __-CFr__ (see below). It |
|
|
1342 |
cannot be used with __-+.__ |
|
|
1343 |
|
|
|
1344 |
|
|
|
1345 |
__-I__ |
|
|
1346 |
|
|
|
1347 |
|
|
|
1348 |
instructs ''flex'' to generate an ''interactive'' |
|
|
1349 |
scanner. An interactive scanner is one that only looks ahead |
|
|
1350 |
to decide what token has been matched if it absolutely must. |
|
|
1351 |
It turns out that always looking one extra character ahead, |
|
|
1352 |
even if the scanner has already seen enough text to |
|
|
1353 |
disambiguate the current token, is a bit faster than only |
|
|
1354 |
looking ahead when necessary. But scanners that always look |
|
|
1355 |
ahead give dreadful interactive performance; for example, |
|
|
1356 |
when a user types a newline, it is not recognized as a |
|
|
1357 |
newline token until they enter ''another'' token, which |
|
|
1358 |
often means typing in another whole line. |
|
|
1359 |
|
|
|
1360 |
|
|
|
1361 |
''Flex'' scanners default to ''interactive'' unless |
|
|
1362 |
you use the __-Cf__ or __-CF__ table-compression |
|
|
1363 |
options (see below). That's because if you're looking for |
|
|
1364 |
high-performance you should be using one of these options, |
|
|
1365 |
so if you didn't, ''flex'' assumes you'd rather trade off |
|
|
1366 |
a bit of run-time performance for intuitive interactive |
|
|
1367 |
behavior. Note also that you ''cannot'' use __-I__ in |
|
|
1368 |
conjunction with __-Cf__ or __-CF.__ Thus, this option |
|
|
1369 |
is not really needed; it is on by default for all those |
|
|
1370 |
cases in which it is allowed. |
|
|
1371 |
|
|
|
1372 |
|
|
|
1373 |
You can force a scanner to ''not'' be interactive by |
|
|
1374 |
using __-B__ (see above). |
|
|
1375 |
|
|
|
1376 |
|
|
|
1377 |
__-L__ |
|
|
1378 |
|
|
|
1379 |
|
|
|
1380 |
instructs ''flex'' not to generate __#line__ |
|
|
1381 |
directives. Without this option, ''flex'' peppers the |
|
|
1382 |
generated scanner with #line directives so error messages in |
|
|
1383 |
the actions will be correctly located with respect to either |
|
|
1384 |
the original ''flex'' input file (if the errors are due |
|
|
1385 |
to code in the input file), or __lex.yy.c__ (if the |
|
|
1386 |
errors are ''flex's'' fault -- you should report these |
|
|
1387 |
sorts of errors to the email address given |
|
|
1388 |
below). |
|
|
1389 |
|
|
|
1390 |
|
|
|
1391 |
__-T__ |
|
|
1392 |
|
|
|
1393 |
|
|
|
1394 |
makes ''flex'' run in ''trace'' mode. It will generate |
|
|
1395 |
a lot of messages to ''stderr'' concerning the form of |
|
|
1396 |
the input and the resultant non-deterministic and |
|
|
1397 |
deterministic finite automata. This option is mostly for use |
|
|
1398 |
in maintaining ''flex.'' |
|
|
1399 |
|
|
|
1400 |
|
|
|
1401 |
__-V__ |
|
|
1402 |
|
|
|
1403 |
|
|
|
1404 |
prints the version number to ''stdout'' and exits. |
|
|
1405 |
__--version__ is a synonym for __-V.__ |
|
|
1406 |
|
|
|
1407 |
|
|
|
1408 |
__-7__ |
|
|
1409 |
|
|
|
1410 |
|
|
|
1411 |
instructs ''flex'' to generate a 7-bit scanner, i.e., one |
|
|
1412 |
which can only recognized 7-bit characters in its input. The |
|
|
1413 |
advantage of using __-7__ is that the scanner's tables |
|
|
1414 |
can be up to half the size of those generated using the |
|
|
1415 |
__-8__ option (see below). The disadvantage is that such |
|
|
1416 |
scanners often hang or crash if their input contains an |
|
|
1417 |
8-bit character. |
|
|
1418 |
|
|
|
1419 |
|
|
|
1420 |
Note, however, that unless you generate your scanner using |
|
|
1421 |
the __-Cf__ or __-CF__ table compression options, use |
|
|
1422 |
of __-7__ will save only a small amount of table space, |
|
|
1423 |
and make your scanner considerably less portable. |
|
|
1424 |
''Flex's'' default behavior is to generate an 8-bit |
|
|
1425 |
scanner unless you use the __-Cf__ or __-CF,__ in |
|
|
1426 |
which case ''flex'' defaults to generating 7-bit scanners |
|
|
1427 |
unless your site was always configured to generate 8-bit |
|
|
1428 |
scanners (as will often be the case with non-USA sites). You |
|
|
1429 |
can tell whether flex generated a 7-bit or an 8-bit scanner |
|
|
1430 |
by inspecting the flag summary in the __-v__ output as |
|
|
1431 |
described above. |
|
|
1432 |
|
|
|
1433 |
|
|
|
1434 |
Note that if you use __-Cfe__ or __-CFe__ (those table |
|
|
1435 |
compression options, but also using equivalence classes as |
|
|
1436 |
discussed see below), flex still defaults to generating an |
|
|
1437 |
8-bit scanner, since usually with these compression options |
|
|
1438 |
full 8-bit tables are not much more expensive than 7-bit |
|
|
1439 |
tables. |
|
|
1440 |
|
|
|
1441 |
|
|
|
1442 |
__-8__ |
|
|
1443 |
|
|
|
1444 |
|
|
|
1445 |
instructs ''flex'' to generate an 8-bit scanner, i.e., |
|
|
1446 |
one which can recognize 8-bit characters. This flag is only |
|
|
1447 |
needed for scanners generated using __-Cf__ or |
|
|
1448 |
__-CF,__ as otherwise flex defaults to generating an |
|
|
1449 |
8-bit scanner anyway. |
|
|
1450 |
|
|
|
1451 |
|
|
|
1452 |
See the discussion of __-7__ above for flex's default |
|
|
1453 |
behavior and the tradeoffs between 7-bit and 8-bit |
|
|
1454 |
scanners. |
|
|
1455 |
|
|
|
1456 |
|
|
|
1457 |
__-+__ |
|
|
1458 |
|
|
|
1459 |
|
|
|
1460 |
specifies that you want flex to generate a C++ scanner |
|
|
1461 |
class. See the section on Generating C++ Scanners below for |
|
|
1462 |
details. |
|
|
1463 |
|
|
|
1464 |
|
|
|
1465 |
__-C[[aefFmr]__ |
|
|
1466 |
|
|
|
1467 |
|
|
|
1468 |
controls the degree of table compression and, more |
|
|
1469 |
generally, trade-offs between small scanners and fast |
|
|
1470 |
scanners. |
|
|
1471 |
|
|
|
1472 |
|
|
|
1473 |
__-Ca__ ( |
|
|
1474 |
__ |
|
|
1475 |
|
|
|
1476 |
|
|
|
1477 |
__-Ce__ directs ''flex'' to construct ''equivalence |
|
|
1478 |
classes,'' i.e., sets of characters which have identical |
|
|
1479 |
lexical properties (for example, if the only appearance of |
|
|
1480 |
digits in the ''flex'' input is in the character class |
|
|
1481 |
'' |
|
|
1482 |
|
|
|
1483 |
|
|
|
1484 |
__-Cf__ specifies that the ''full'' scanner tables |
|
|
1485 |
should be generated - ''flex'' should not compress the |
|
|
1486 |
tables by taking advantages of similar transition functions |
|
|
1487 |
for different states. |
|
|
1488 |
|
|
|
1489 |
|
|
|
1490 |
__-CF__ specifies that the alternate fast scanner |
|
|
1491 |
representation (described above under the __-F__ flag) |
|
|
1492 |
should be used. This option cannot be used with |
|
|
1493 |
__-+.__ |
|
|
1494 |
|
|
|
1495 |
|
|
|
1496 |
__-Cm__ directs ''flex'' to construct |
|
|
1497 |
''meta-equivalence classes,'' which are sets of |
|
|
1498 |
equivalence classes (or characters, if equivalence classes |
|
|
1499 |
are not being used) that are commonly used together. |
|
|
1500 |
Meta-equivalence classes are often a big win when using |
|
|
1501 |
compressed tables, but they have a moderate performance |
|
|
1502 |
impact (one or two |
|
|
1503 |
'' |
|
|
1504 |
|
|
|
1505 |
|
|
|
1506 |
__-Cr__ causes the generated scanner to ''bypass'' use |
|
|
1507 |
of the standard I/O library (stdio) for input. Instead of |
|
|
1508 |
calling __fread()__ or __getc(),__ the scanner will |
|
|
1509 |
use the __read()__ system call, resulting in a |
|
|
1510 |
performance gain which varies from system to system, but in |
|
|
1511 |
general is probably negligible unless you are also using |
|
|
1512 |
__-Cf__ or __-CF.__ Using __-Cr__ can cause strange |
|
|
1513 |
behavior if, for example, you read from ''yyin'' using |
|
|
1514 |
stdio prior to calling the scanner (because the scanner will |
|
|
1515 |
miss whatever text your previous reads left in the stdio |
|
|
1516 |
input buffer). |
|
|
1517 |
|
|
|
1518 |
|
|
|
1519 |
__-Cr__ has no effect if you define __YY_INPUT__ (see |
|
|
1520 |
The Generated Scanner above). |
|
|
1521 |
|
|
|
1522 |
|
|
|
1523 |
A lone __-C__ specifies that the scanner tables should be |
|
|
1524 |
compressed but neither equivalence classes nor |
|
|
1525 |
meta-equivalence classes should be used. |
|
|
1526 |
|
|
|
1527 |
|
|
|
1528 |
The options __-Cf__ or __-CF__ and __-Cm__ do not |
|
|
1529 |
make sense together - there is no opportunity for |
|
|
1530 |
meta-equivalence classes if the table is not being |
|
|
1531 |
compressed. Otherwise the options may be freely mixed, and |
|
|
1532 |
are cumulative. |
|
|
1533 |
|
|
|
1534 |
|
|
|
1535 |
The default setting is __-Cem,__ which specifies that |
|
|
1536 |
''flex'' should generate equivalence classes and |
|
|
1537 |
meta-equivalence classes. This setting provides the highest |
|
|
1538 |
degree of table compression. You can trade off |
|
|
1539 |
faster-executing scanners at the cost of larger tables with |
|
|
1540 |
the following generally being true: |
|
|
1541 |
|
|
|
1542 |
|
|
|
1543 |
slowest |
|
|
1544 |
Note that scanners with the smallest tables are usually generated and compiled the quickest, so during development you will usually want to use the default, maximal compression. |
|
|
1545 |
|
|
|
1546 |
|
|
|
1547 |
__-Cfe__ is often a good compromise between speed and |
|
|
1548 |
size for production scanners. |
|
|
1549 |
|
|
|
1550 |
|
|
|
1551 |
__-ooutput__ |
|
|
1552 |
|
|
|
1553 |
|
|
|
1554 |
directs flex to write the scanner to the file __output__ |
|
|
1555 |
instead of __lex.yy.c.__ If you combine __-o__ with |
|
|
1556 |
the __-t__ option, then the scanner is written to |
|
|
1557 |
''stdout'' but its __#line__ directives (see the |
|
|
1558 |
__-L__ option above) refer to the file |
|
|
1559 |
__output.__ |
|
|
1560 |
|
|
|
1561 |
|
|
|
1562 |
__-Pprefix__ |
|
|
1563 |
|
|
|
1564 |
|
|
|
1565 |
changes the default ''yy'' prefix used by ''flex'' for |
|
|
1566 |
all globally-visible variable and function names to instead |
|
|
1567 |
be ''prefix.'' For example, __-Pfoo__ changes the name |
|
|
1568 |
of __yytext__ to __footext.__ It also changes the name |
|
|
1569 |
of the default output file from __lex.yy.c__ to |
|
|
1570 |
__lex.foo.c.__ Here are all of the names |
|
|
1571 |
affected: |
|
|
1572 |
|
|
|
1573 |
|
|
|
1574 |
yy_create_buffer |
|
|
1575 |
yy_delete_buffer |
|
|
1576 |
yy_flex_debug |
|
|
1577 |
yy_init_buffer |
|
|
1578 |
yy_flush_buffer |
|
|
1579 |
yy_load_buffer_state |
|
|
1580 |
yy_switch_to_buffer |
|
|
1581 |
yyin |
|
|
1582 |
yyleng |
|
|
1583 |
yylex |
|
|
1584 |
yylineno |
|
|
1585 |
yyout |
|
|
1586 |
yyrestart |
|
|
1587 |
yytext |
|
|
1588 |
yywrap |
|
|
1589 |
(If you are using a C++ scanner, then only __yywrap__ and __yyFlexLexer__ are affected.) Within your scanner itself, you can still refer to the global variables and functions using either version of their name; but externally, they have the modified name. |
|
|
1590 |
|
|
|
1591 |
|
|
|
1592 |
This option lets you easily link together multiple |
|
|
1593 |
''flex'' programs into the same executable. Note, though, |
|
|
1594 |
that using this option also renames __yywrap(),__ so you |
|
|
1595 |
now ''must'' either provide your own |
|
|
1596 |
(appropriately-named) version of the routine for your |
|
|
1597 |
scanner, or use __%option noyywrap,__ as linking with |
|
|
1598 |
__-lfl__ no longer provides one for you by |
|
|
1599 |
default. |
|
|
1600 |
|
|
|
1601 |
|
|
|
1602 |
__-Sskeleton_file__ |
|
|
1603 |
|
|
|
1604 |
|
|
|
1605 |
overrides the default skeleton file from which ''flex'' |
|
|
1606 |
constructs its scanners. You'll never need this option |
|
|
1607 |
unless you are doing ''flex'' maintenance or |
|
|
1608 |
development. |
|
|
1609 |
|
|
|
1610 |
|
|
|
1611 |
''flex'' also provides a mechanism for controlling |
|
|
1612 |
options within the scanner specification itself, rather than |
|
|
1613 |
from the flex command-line. This is done by including |
|
|
1614 |
__%option__ directives in the first section of the |
|
|
1615 |
scanner specification. You can specify multiple options with |
|
|
1616 |
a single __%option__ directive, and multiple directives |
|
|
1617 |
in the first section of your flex input file. |
|
|
1618 |
|
|
|
1619 |
|
|
|
1620 |
Most options are given simply as names, optionally preceded |
|
|
1621 |
by the word |
|
|
1622 |
|
|
|
1623 |
|
|
|
1624 |
7bit -7 option |
|
|
1625 |
8bit -8 option |
|
|
1626 |
align -Ca option |
|
|
1627 |
backup -b option |
|
|
1628 |
batch -B option |
|
|
1629 |
c++ -+ option |
|
|
1630 |
caseful or |
|
|
1631 |
case-sensitive opposite of -i (default) |
|
|
1632 |
case-insensitive or |
|
|
1633 |
caseless -i option |
|
|
1634 |
debug -d option |
|
|
1635 |
default opposite of -s option |
|
|
1636 |
ecs -Ce option |
|
|
1637 |
fast -F option |
|
|
1638 |
full -f option |
|
|
1639 |
interactive -I option |
|
|
1640 |
lex-compat -l option |
|
|
1641 |
meta-ecs -Cm option |
|
|
1642 |
perf-report -p option |
|
|
1643 |
read -Cr option |
|
|
1644 |
stdout -t option |
|
|
1645 |
verbose -v option |
|
|
1646 |
warn opposite of -w option |
|
|
1647 |
(use |
|
|
1648 |
Some __%option's__ provide features otherwise not available: |
|
|
1649 |
|
|
|
1650 |
|
|
|
1651 |
__always-interactive__ |
|
|
1652 |
|
|
|
1653 |
|
|
|
1654 |
instructs flex to generate a scanner which always considers |
|
|
1655 |
its input |
|
|
1656 |
isatty()__ in an attempt |
|
|
1657 |
to determine whether the scanner's input source is |
|
|
1658 |
interactive and thus should be read a character at a time. |
|
|
1659 |
When this option is used, however, then no such call is |
|
|
1660 |
made. |
|
|
1661 |
|
|
|
1662 |
|
|
|
1663 |
__main__ |
|
|
1664 |
|
|
|
1665 |
|
|
|
1666 |
directs flex to provide a default __main()__ program for |
|
|
1667 |
the scanner, which simply calls __yylex().__ This option |
|
|
1668 |
implies __noyywrap__ (see below). |
|
|
1669 |
|
|
|
1670 |
|
|
|
1671 |
__never-interactive__ |
|
|
1672 |
|
|
|
1673 |
|
|
|
1674 |
instructs flex to generate a scanner which never considers |
|
|
1675 |
its input |
|
|
1676 |
isatty()).__ This is the opposite of |
|
|
1677 |
__always-interactive.__ |
|
|
1678 |
|
|
|
1679 |
|
|
|
1680 |
__stack__ |
|
|
1681 |
|
|
|
1682 |
|
|
|
1683 |
enables the use of start condition stacks (see Start |
|
|
1684 |
Conditions above). |
|
|
1685 |
|
|
|
1686 |
|
|
|
1687 |
__stdinit__ |
|
|
1688 |
|
|
|
1689 |
|
|
|
1690 |
if set (i.e., __%option stdinit)__ initializes |
|
|
1691 |
''yyin'' and ''yyout'' to ''stdin'' and |
|
|
1692 |
''stdout,'' instead of the default of ''nil.'' Some |
|
|
1693 |
existing ''lex'' programs depend on this behavior, even |
|
|
1694 |
though it is not compliant with ANSI C, which does not |
|
|
1695 |
require ''stdin'' and ''stdout'' to be compile-time |
|
|
1696 |
constant. In a reentrant scanner, however, this is not a |
|
|
1697 |
problem since initialization is performed in |
|
|
1698 |
''yylex_init'' at runtime. |
|
|
1699 |
|
|
|
1700 |
|
|
|
1701 |
__yylineno__ |
|
|
1702 |
|
|
|
1703 |
|
|
|
1704 |
directs ''flex'' to generate a scanner that maintains the |
|
|
1705 |
number of the current line read from its input in the global |
|
|
1706 |
variable __yylineno.__ This option is implied by |
|
|
1707 |
__%option lex-compat.__ |
|
|
1708 |
|
|
|
1709 |
|
|
|
1710 |
__yywrap__ |
|
|
1711 |
|
|
|
1712 |
|
|
|
1713 |
if unset (i.e., __%option noyywrap),__ makes the scanner |
|
|
1714 |
not call __yywrap()__ upon an end-of-file, but simply |
|
|
1715 |
assume that there are no more files to scan (until the user |
|
|
1716 |
points ''yyin'' at a new file and calls __yylex()__ |
|
|
1717 |
again). |
|
|
1718 |
|
|
|
1719 |
|
|
|
1720 |
''flex'' scans your rule actions to determine whether you |
|
|
1721 |
use the __REJECT__ or __yymore()__ features. The |
|
|
1722 |
__reject__ and __yymore__ options are available to |
|
|
1723 |
override its decision as to whether you use the options, |
|
|
1724 |
either by setting them (e.g., __%option reject)__ to |
|
|
1725 |
indicate the feature is indeed used, or unsetting them to |
|
|
1726 |
indicate it actually is not used (e.g., __%option |
|
|
1727 |
noyymore).__ |
|
|
1728 |
|
|
|
1729 |
|
|
|
1730 |
Three options take string-delimited values, offset with |
|
|
1731 |
'=': |
|
|
1732 |
|
|
|
1733 |
|
|
|
1734 |
%option outfile= |
|
|
1735 |
is equivalent to __-oABC,__ and |
|
|
1736 |
|
|
|
1737 |
|
|
|
1738 |
%option prefix= |
|
|
1739 |
is equivalent to __-PXYZ.__ Finally, |
|
|
1740 |
|
|
|
1741 |
|
|
|
1742 |
%option yyclass= |
2 |
perry |
1743 |
only applies when generating a C++ scanner ( __-+__ option). It informs ''flex'' that you have derived __foo__ as a subclass of __yyFlexLexer,__ so ''flex'' will place your actions in the member function __foo::yylex()__ instead of __yyFlexLexer::yylex().__ It also generates a __yyFlexLexer::yylex()__ member function that emits a run-time error (by invoking __yyFlexLexer::!LexerError())__ if called. See Generating C++ Scanners, below, for additional information. |
1 |
perry |
1744 |
|
|
|
1745 |
|
|
|
1746 |
A number of options are available for lint purists who want |
|
|
1747 |
to suppress the appearance of unneeded routines in the |
|
|
1748 |
generated scanner. Each of the following, if unset (e.g., |
|
|
1749 |
__%option nounput__ ), results in the corresponding |
|
|
1750 |
routine not appearing in the generated scanner: |
|
|
1751 |
|
|
|
1752 |
|
|
|
1753 |
input, unput |
|
|
1754 |
yy_push_state, yy_pop_state, yy_top_state |
|
|
1755 |
yy_scan_buffer, yy_scan_bytes, yy_scan_string |
|
|
1756 |
(though __yy_push_state()__ and friends won't appear anyway unless you use __%option stack).__ |
|
|
1757 |
!!PERFORMANCE CONSIDERATIONS |
|
|
1758 |
|
|
|
1759 |
|
|
|
1760 |
The main design goal of ''flex'' is that it generate |
|
|
1761 |
high-performance scanners. It has been optimized for dealing |
|
|
1762 |
well with large sets of rules. Aside from the effects on |
|
|
1763 |
scanner speed of the table compression __-C__ options |
|
|
1764 |
outlined above, there are a number of options/actions which |
|
|
1765 |
degrade performance. These are, from most expensive to |
|
|
1766 |
least: |
|
|
1767 |
|
|
|
1768 |
|
|
|
1769 |
REJECT |
|
|
1770 |
%option yylineno |
|
|
1771 |
arbitrary trailing context |
|
|
1772 |
pattern sets that require backing up |
|
|
1773 |
%array |
|
|
1774 |
%option interactive |
|
|
1775 |
%option always-interactive |
|
|
1776 |
'^' beginning-of-line operator |
|
|
1777 |
yymore() |
|
|
1778 |
with the first three all being quite expensive and the last two being quite cheap. Note also that __unput()__ is implemented as a routine call that potentially does quite a bit of work, while __yyless()__ is a quite-cheap macro; so if just putting back some excess text you scanned, use __yyless().__ |
|
|
1779 |
|
|
|
1780 |
|
|
|
1781 |
__REJECT__ should be avoided at all costs when |
|
|
1782 |
performance is important. It is a particularly expensive |
|
|
1783 |
option. |
|
|
1784 |
|
|
|
1785 |
|
|
|
1786 |
Getting rid of backing up is messy and often may be an |
|
|
1787 |
enormous amount of work for a complicated scanner. In |
|
|
1788 |
principal, one begins by using the __-b__ flag to |
|
|
1789 |
generate a ''lex.backup'' file. For example, on the |
|
|
1790 |
input |
|
|
1791 |
|
|
|
1792 |
|
|
|
1793 |
%% |
|
|
1794 |
foo return TOK_KEYWORD; |
|
|
1795 |
foobar return TOK_KEYWORD; |
|
|
1796 |
the file looks like: |
|
|
1797 |
|
|
|
1798 |
|
|
|
1799 |
State #6 is non-accepting - |
|
|
1800 |
associated rule line numbers: |
|
|
1801 |
2 3 |
|
|
1802 |
out-transitions: [[ o ] |
|
|
1803 |
jam-transitions: EOF [[ 001-n p-177 ] |
|
|
1804 |
State #8 is non-accepting - |
|
|
1805 |
associated rule line numbers: |
|
|
1806 |
3 |
|
|
1807 |
out-transitions: [[ a ] |
|
|
1808 |
jam-transitions: EOF [[ 001-` b-177 ] |
|
|
1809 |
State #9 is non-accepting - |
|
|
1810 |
associated rule line numbers: |
|
|
1811 |
3 |
|
|
1812 |
out-transitions: [[ r ] |
|
|
1813 |
jam-transitions: EOF [[ 001-q s-177 ] |
|
|
1814 |
Compressed tables always back up. |
|
|
1815 |
The first few lines tell us that there's a scanner state in which it can make a transition on an 'o' but not on any other character, and that in that state the currently scanned text does not match any rule. The state occurs when trying to match the rules found at lines 2 and 3 in the input file. If the scanner is in that state and then reads something other than an 'o', it will have to back up to find a rule which is matched. With a bit of headscratching one can see that this must be the state it's in when it has seen |
|
|
1816 |
|
|
|
1817 |
|
|
|
1818 |
The comment regarding State #8 indicates there's a problem |
|
|
1819 |
when |
|
|
1820 |
|
|
|
1821 |
|
|
|
1822 |
The final comment reminds us that there's no point going to |
|
|
1823 |
all the trouble of removing backing up from the rules unless |
|
|
1824 |
we're using __-Cf__ or __-CF,__ since there's no |
|
|
1825 |
performance gain doing so with compressed |
|
|
1826 |
scanners. |
|
|
1827 |
|
|
|
1828 |
|
|
|
1829 |
The way to remove the backing up is to add |
|
|
1830 |
|
|
|
1831 |
|
|
|
1832 |
%% |
|
|
1833 |
foo return TOK_KEYWORD; |
|
|
1834 |
foobar return TOK_KEYWORD; |
|
|
1835 |
fooba | |
|
|
1836 |
foob | |
|
|
1837 |
fo { |
|
|
1838 |
/* false alarm, not really a keyword */ |
|
|
1839 |
return TOK_ID; |
|
|
1840 |
} |
|
|
1841 |
Eliminating backing up among a list of keywords can also be done using a |
|
|
1842 |
|
|
|
1843 |
|
|
|
1844 |
%% |
|
|
1845 |
foo return TOK_KEYWORD; |
|
|
1846 |
foobar return TOK_KEYWORD; |
|
|
1847 |
[[a-z]+ return TOK_ID; |
|
|
1848 |
This is usually the best solution when appropriate. |
|
|
1849 |
|
|
|
1850 |
|
|
|
1851 |
Backing up messages tend to cascade. With a complicated set |
|
|
1852 |
of rules it's not uncommon to get hundreds of messages. If |
|
|
1853 |
one can decipher them, though, it often only takes a dozen |
|
|
1854 |
or so rules to eliminate the backing up (though it's easy to |
|
|
1855 |
make a mistake and have an error rule accidentally match a |
|
|
1856 |
valid token. A possible future ''flex'' feature will be |
|
|
1857 |
to automatically add rules to eliminate backing |
|
|
1858 |
up). |
|
|
1859 |
|
|
|
1860 |
|
|
|
1861 |
It's important to keep in mind that you gain the benefits of |
|
|
1862 |
eliminating backing up only if you eliminate ''every'' |
|
|
1863 |
instance of backing up. Leaving just one means you gain |
|
|
1864 |
nothing. |
|
|
1865 |
|
|
|
1866 |
|
|
|
1867 |
''Variable'' trailing context (where both the leading and |
|
|
1868 |
trailing parts do not have a fixed length) entails almost |
|
|
1869 |
the same performance loss as __REJECT__ (i.e., |
|
|
1870 |
substantial). So when possible a rule like: |
|
|
1871 |
|
|
|
1872 |
|
|
|
1873 |
%% |
|
|
1874 |
mouse|rat/(cat|dog) run(); |
|
|
1875 |
is better written: |
|
|
1876 |
|
|
|
1877 |
|
|
|
1878 |
%% |
|
|
1879 |
mouse/cat|dog run(); |
|
|
1880 |
rat/cat|dog run(); |
|
|
1881 |
or as |
|
|
1882 |
|
|
|
1883 |
|
|
|
1884 |
%% |
|
|
1885 |
mouse|rat/cat run(); |
|
|
1886 |
mouse|rat/dog run(); |
|
|
1887 |
Note that here the special '|' action does ''not'' provide any savings, and can even make things worse (see Deficiencies / Bugs below). |
|
|
1888 |
|
|
|
1889 |
|
|
|
1890 |
Another area where the user can increase a scanner's |
|
|
1891 |
performance (and one that's easier to implement) arises from |
|
|
1892 |
the fact that the longer the tokens matched, the faster the |
|
|
1893 |
scanner will run. This is because with long tokens the |
|
|
1894 |
processing of most input characters takes place in the |
|
|
1895 |
(short) inner scanning loop, and does not often have to go |
|
|
1896 |
through the additional work of setting up the scanning |
|
|
1897 |
environment (e.g., __yytext)__ for the action. Recall the |
|
|
1898 |
scanner for C comments: |
|
|
1899 |
|
|
|
1900 |
|
|
|
1901 |
%x comment |
|
|
1902 |
%% |
|
|
1903 |
int line_num = 1; |
|
|
1904 |
This could be sped up by writing it as: |
|
|
1905 |
|
|
|
1906 |
|
|
|
1907 |
%x comment |
|
|
1908 |
%% |
|
|
1909 |
int line_num = 1; |
|
|
1910 |
Now instead of each newline requiring the processing of another action, recognizing the newlines is adding'' rules does ''not'' slow down the scanner! The speed of the scanner is independent of the number of rules or (modulo the considerations given at the beginning of this section) how complicated the rules are with regard to operators such as '*' and '|'. |
|
|
1911 |
|
|
|
1912 |
|
|
|
1913 |
A final example in speeding up a scanner: suppose you want |
|
|
1914 |
to scan through a file containing identifiers and keywords, |
|
|
1915 |
one per line and with no other extraneous characters, and |
|
|
1916 |
recognize all the keywords. A natural first approach |
|
|
1917 |
is: |
|
|
1918 |
|
|
|
1919 |
|
|
|
1920 |
%% |
|
|
1921 |
asm | |
|
|
1922 |
auto | |
|
|
1923 |
break | |
|
|
1924 |
... etc ... |
|
|
1925 |
volatile | |
|
|
1926 |
while /* it's a keyword */ |
|
|
1927 |
.|n /* it's not a keyword */ |
|
|
1928 |
To eliminate the back-tracking, introduce a catch-all rule: |
|
|
1929 |
|
|
|
1930 |
|
|
|
1931 |
%% |
|
|
1932 |
asm | |
|
|
1933 |
auto | |
|
|
1934 |
break | |
|
|
1935 |
... etc ... |
|
|
1936 |
volatile | |
|
|
1937 |
while /* it's a keyword */ |
|
|
1938 |
[[a-z]+ | |
|
|
1939 |
.|n /* it's not a keyword */ |
|
|
1940 |
Now, if it's guaranteed that there's exactly one word per line, then we can reduce the total number of matches by a half by merging in the recognition of newlines with that of the other tokens: |
|
|
1941 |
|
|
|
1942 |
|
|
|
1943 |
%% |
|
|
1944 |
asmn | |
|
|
1945 |
auton | |
|
|
1946 |
breakn | |
|
|
1947 |
... etc ... |
|
|
1948 |
volatilen | |
|
|
1949 |
whilen /* it's a keyword */ |
|
|
1950 |
[[a-z]+n | |
|
|
1951 |
.|n /* it's not a keyword */ |
|
|
1952 |
One has to be careful here, as we have now reintroduced backing up into the scanner. In particular, while ''we'' know that there will never be any characters in the input stream other than letters or newlines, ''flex'' can't figure this out, and it will plan for possibly needing to back up when it has scanned a token like '' |
|
|
1953 |
|
|
|
1954 |
|
|
|
1955 |
%% |
|
|
1956 |
asmn | |
|
|
1957 |
auton | |
|
|
1958 |
breakn | |
|
|
1959 |
... etc ... |
|
|
1960 |
volatilen | |
|
|
1961 |
whilen /* it's a keyword */ |
|
|
1962 |
[[a-z]+n | |
|
|
1963 |
[[a-z]+ | |
|
|
1964 |
.|n /* it's not a keyword */ |
|
|
1965 |
Compiled with __-Cf,__ this is about as fast as one can get a ''flex'' scanner to go for this particular problem. |
|
|
1966 |
|
|
|
1967 |
|
|
|
1968 |
A final note: ''flex'' is slow when matching NUL's, |
|
|
1969 |
particularly when a token contains multiple NUL's. It's best |
|
|
1970 |
to write rules which match ''short'' amounts of text if |
|
|
1971 |
it's anticipated that the text will often include |
|
|
1972 |
NUL's. |
|
|
1973 |
|
|
|
1974 |
|
|
|
1975 |
Another final note regarding performance: as mentioned above |
|
|
1976 |
in the section How the Input is Matched, dynamically |
|
|
1977 |
resizing __yytext__ to accommodate huge tokens is a slow |
|
|
1978 |
process because it presently requires that the (huge) token |
|
|
1979 |
be rescanned from the beginning. Thus if performance is |
|
|
1980 |
vital, you should attempt to match |
|
|
1981 |
__ |
|
|
1982 |
!!GENERATING C++ SCANNERS |
|
|
1983 |
|
|
|
1984 |
|
|
|
1985 |
''flex'' provides two different ways to generate scanners |
|
|
1986 |
for use with C++. The first way is to simply compile a |
|
|
1987 |
scanner generated by ''flex'' using a C++ compiler |
|
|
1988 |
instead of a C compiler. You should not encounter any |
|
|
1989 |
compilations errors (please report any you find to the email |
|
|
1990 |
address given in the Author section below). You can then use |
|
|
1991 |
C++ code in your rule actions instead of C code. Note that |
|
|
1992 |
the default input source for your scanner remains |
|
|
1993 |
''yyin,'' and default echoing is still done to |
|
|
1994 |
''yyout.'' Both of these remain ''FILE *'' variables |
|
|
1995 |
and not C++ ''streams.'' |
|
|
1996 |
|
|
|
1997 |
|
|
|
1998 |
You can also use ''flex'' to generate a C++ scanner |
|
|
1999 |
class, using the __-+__ option (or, equivalently, |
|
|
2000 |
__%option c++),__ which is automatically specified if the |
|
|
2001 |
name of the flex executable ends in a '+', such as |
|
|
2002 |
''flex++.'' When using this option, flex defaults to |
|
|
2003 |
generating the scanner to the file __lex.yy.cc__ instead |
|
|
2004 |
of __lex.yy.c.__ The generated scanner includes the |
2 |
perry |
2005 |
header file ''!FlexLexer.h,'' which defines the interface |
1 |
perry |
2006 |
to two C++ classes. |
|
|
2007 |
|
|
|
2008 |
|
2 |
perry |
2009 |
The first class, __!FlexLexer,__ provides an abstract base |
1 |
perry |
2010 |
class defining the general scanner class interface. It |
|
|
2011 |
provides the following member functions: |
|
|
2012 |
|
|
|
2013 |
|
|
|
2014 |
__const char* YYText()__ |
|
|
2015 |
|
|
|
2016 |
|
|
|
2017 |
returns the text of the most recently matched token, the |
|
|
2018 |
equivalent of __yytext.__ |
|
|
2019 |
|
|
|
2020 |
|
|
|
2021 |
__int YYLeng()__ |
|
|
2022 |
|
|
|
2023 |
|
|
|
2024 |
returns the length of the most recently matched token, the |
|
|
2025 |
equivalent of __yyleng.__ |
|
|
2026 |
|
|
|
2027 |
|
|
|
2028 |
__int lineno() const__ |
|
|
2029 |
|
|
|
2030 |
|
|
|
2031 |
returns the current input line number (see __%option |
|
|
2032 |
yylineno),__ or __1__ if __%option yylineno__ was |
|
|
2033 |
not used. |
|
|
2034 |
|
|
|
2035 |
|
|
|
2036 |
__void set_debug( int flag )__ |
|
|
2037 |
|
|
|
2038 |
|
|
|
2039 |
sets the debugging flag for the scanner, equivalent to |
|
|
2040 |
assigning to __yy_flex_debug__ (see the Options section |
|
|
2041 |
above). Note that you must build the scanner using |
|
|
2042 |
__%option debug__ to include debugging information in |
|
|
2043 |
it. |
|
|
2044 |
|
|
|
2045 |
|
|
|
2046 |
__int debug() const__ |
|
|
2047 |
|
|
|
2048 |
|
|
|
2049 |
returns the current setting of the debugging |
|
|
2050 |
flag. |
|
|
2051 |
|
|
|
2052 |
|
|
|
2053 |
Also provided are member functions equivalent to |
|
|
2054 |
__yy_switch_to_buffer(), yy_create_buffer()__ (though the |
|
|
2055 |
first argument is an __istream*__ object pointer and not |
|
|
2056 |
a __FILE*), yy_flush_buffer(), yy_delete_buffer(),__ and |
|
|
2057 |
__yyrestart()__ (again, the first argument is a |
|
|
2058 |
__istream*__ object pointer). |
|
|
2059 |
|
|
|
2060 |
|
2 |
perry |
2061 |
The second class defined in ''!FlexLexer.h'' is |
|
|
2062 |
__yyFlexLexer,__ which is derived from __!FlexLexer.__ |
1 |
perry |
2063 |
It defines the following additional member |
|
|
2064 |
functions: |
|
|
2065 |
|
|
|
2066 |
|
|
|
2067 |
__yyFlexLexer( istream* arg_yyin = 0, ostream* arg_yyout = |
|
|
2068 |
0 )__ |
|
|
2069 |
|
|
|
2070 |
|
|
|
2071 |
constructs a __yyFlexLexer__ object using the given |
|
|
2072 |
streams for input and output. If not specified, the streams |
|
|
2073 |
default to __cin__ and __cout,__ |
|
|
2074 |
respectively. |
|
|
2075 |
|
|
|
2076 |
|
|
|
2077 |
__virtual int yylex()__ |
|
|
2078 |
|
|
|
2079 |
|
|
|
2080 |
performs the same role is __yylex()__ does for ordinary |
|
|
2081 |
flex scanners: it scans the input stream, consuming tokens, |
|
|
2082 |
until a rule's action returns a value. If you derive a |
|
|
2083 |
subclass __S__ from __yyFlexLexer__ and want to access |
|
|
2084 |
the member functions and variables of __S__ inside |
|
|
2085 |
__yylex(),__ then you need to use __%option |
|
|
2086 |
yyclass=__ to inform ''flex'' that you |
|
|
2087 |
will be using that subclass instead of __yyFlexLexer.__ |
|
|
2088 |
In this case, rather than generating |
|
|
2089 |
__yyFlexLexer::yylex(),__ ''flex'' generates |
|
|
2090 |
__S::yylex()__ (and also generates a dummy |
|
|
2091 |
__yyFlexLexer::yylex()__ that calls |
2 |
perry |
2092 |
__yyFlexLexer::!LexerError()__ if called). |
1 |
perry |
2093 |
|
|
|
2094 |
|
|
|
2095 |
__virtual void switch_streams(istream* new_in = |
|
|
2096 |
0,__ |
|
|
2097 |
|
|
|
2098 |
|
|
|
2099 |
__ostream* new_out = 0)__ reassigns __yyin__ to |
|
|
2100 |
__new_in__ (if non-nil) and __yyout__ to |
|
|
2101 |
__new_out__ (ditto), deleting the previous input buffer |
|
|
2102 |
if __yyin__ is reassigned. |
|
|
2103 |
|
|
|
2104 |
|
|
|
2105 |
__int yylex( istream* new_in, ostream* new_out = 0 |
|
|
2106 |
)__ |
|
|
2107 |
|
|
|
2108 |
|
|
|
2109 |
first switches the input streams via __switch_streams( |
|
|
2110 |
new_in, new_out )__ and then returns the value of |
|
|
2111 |
__yylex().__ |
|
|
2112 |
|
|
|
2113 |
|
|
|
2114 |
In addition, __yyFlexLexer__ defines the following |
|
|
2115 |
protected virtual functions which you can redefine in |
|
|
2116 |
derived classes to tailor the scanner: |
|
|
2117 |
|
|
|
2118 |
|
2 |
perry |
2119 |
__virtual int !LexerInput( char* buf, int max_size |
1 |
perry |
2120 |
)__ |
|
|
2121 |
|
|
|
2122 |
|
|
|
2123 |
reads up to __max_size__ characters into __buf__ and |
|
|
2124 |
returns the number of characters read. To indicate |
|
|
2125 |
end-of-input, return 0 characters. Note that |
|
|
2126 |
__-B__ and |
|
|
2127 |
__-I__ flags) define the macro __YY_INTERACTIVE.__ If |
2 |
perry |
2128 |
you redefine __!LexerInput()__ and need to take different |
1 |
perry |
2129 |
actions depending on whether or not the scanner might be |
|
|
2130 |
scanning an interactive input source, you can test for the |
|
|
2131 |
presence of this name via __#ifdef.__ |
|
|
2132 |
|
|
|
2133 |
|
2 |
perry |
2134 |
__virtual void !LexerOutput( const char* buf, int size |
1 |
perry |
2135 |
)__ |
|
|
2136 |
|
|
|
2137 |
|
|
|
2138 |
writes out __size__ characters from the buffer |
|
|
2139 |
__buf,__ which, while NUL-terminated, may also contain |
|
|
2140 |
__ |
|
|
2141 |
|
|
|
2142 |
|
2 |
perry |
2143 |
__virtual void !LexerError( const char* msg |
1 |
perry |
2144 |
)__ |
|
|
2145 |
|
|
|
2146 |
|
|
|
2147 |
reports a fatal error message. The default version of this |
|
|
2148 |
function writes the message to the stream __cerr__ and |
|
|
2149 |
exits. |
|
|
2150 |
|
|
|
2151 |
|
|
|
2152 |
Note that a __yyFlexLexer__ object contains its |
|
|
2153 |
''entire'' scanning state. Thus you can use such objects |
|
|
2154 |
to create reentrant scanners. You can instantiate multiple |
|
|
2155 |
instances of the same __yyFlexLexer__ class, and you can |
|
|
2156 |
also combine multiple C++ scanner classes together in the |
|
|
2157 |
same program using the __-P__ option discussed |
|
|
2158 |
above. |
|
|
2159 |
|
|
|
2160 |
|
|
|
2161 |
Finally, note that the __%array__ feature is not |
|
|
2162 |
available to C++ scanner classes; you must use |
|
|
2163 |
__%pointer__ (the default). |
|
|
2164 |
|
|
|
2165 |
|
|
|
2166 |
Here is an example of a simple C++ scanner: |
|
|
2167 |
|
|
|
2168 |
|
|
|
2169 |
// An example of using the flex C++ scanner class. |
|
|
2170 |
%{ |
|
|
2171 |
int mylineno = 0; |
|
|
2172 |
%} |
|
|
2173 |
string |
|
|
2174 |
If you want to create multiple (different) lexer classes, you use the __-P__ flag (or the __prefix=__ option) to rename each __yyFlexLexer__ to some other __xxFlexLexer.__ You then can include ____ in your other sources once per lexer class, first renaming __yyFlexLexer__ as follows: |
|
|
2175 |
|
|
|
2176 |
|
|
|
2177 |
#undef yyFlexLexer |
|
|
2178 |
#define yyFlexLexer xxFlexLexer |
|
|
2179 |
#include |
|
|
2180 |
if, for example, you used __%option prefix=__ for one of your scanners and __%option prefix=__ for the other. |
|
|
2181 |
|
|
|
2182 |
|
|
|
2183 |
IMPORTANT: the present form of the scanning class is |
|
|
2184 |
''experimental'' and may change considerably between |
|
|
2185 |
major releases. |
|
|
2186 |
!!INCOMPATIBILITIES WITH LEX AND POSIX |
|
|
2187 |
|
|
|
2188 |
|
|
|
2189 |
''flex'' is a rewrite of the AT''lex'' |
|
|
2190 |
tool (the two implementations do not share any code, |
|
|
2191 |
though), with some extensions and incompatibilities, both of |
|
|
2192 |
which are of concern to those who wish to write scanners |
|
|
2193 |
acceptable to either implementation. Flex is fully compliant |
|
|
2194 |
with the POSIX ''lex'' specification, except that when |
|
|
2195 |
using __%pointer__ (the default), a call to |
|
|
2196 |
__unput()__ destroys the contents of __yytext,__ which |
|
|
2197 |
is counter to the POSIX specification. |
|
|
2198 |
|
|
|
2199 |
|
|
|
2200 |
In this section we discuss all of the known areas of |
|
|
2201 |
incompatibility between flex, AT |
|
|
2202 |
|
|
|
2203 |
|
|
|
2204 |
''flex's'' __-l__ option turns on maximum |
|
|
2205 |
compatibility with the original AT__lex'' |
|
|
2206 |
implementation, at the cost of a major loss in the generated |
|
|
2207 |
scanner's performance. We note below which incompatibilities |
|
|
2208 |
can be overcome using the __-l__ option. |
|
|
2209 |
|
|
|
2210 |
|
|
|
2211 |
''flex'' is fully compatible with ''lex'' with the |
|
|
2212 |
following exceptions: |
|
|
2213 |
|
|
|
2214 |
|
|
|
2215 |
- |
|
|
2216 |
|
|
|
2217 |
|
|
|
2218 |
The undocumented ''lex'' scanner internal variable |
|
|
2219 |
__yylineno__ is not supported unless __-l__ or |
|
|
2220 |
__%option yylineno__ is used. |
|
|
2221 |
|
|
|
2222 |
|
|
|
2223 |
__yylineno__ should be maintained on a per-buffer basis, |
|
|
2224 |
rather than a per-scanner (single global variable) |
|
|
2225 |
basis. |
|
|
2226 |
|
|
|
2227 |
|
|
|
2228 |
__yylineno__ is not part of the POSIX |
|
|
2229 |
specification. |
|
|
2230 |
|
|
|
2231 |
|
|
|
2232 |
- |
|
|
2233 |
|
|
|
2234 |
|
|
|
2235 |
The __input()__ routine is not redefinable, though it may |
|
|
2236 |
be called to read characters following whatever has been |
|
|
2237 |
matched by a rule. If __input()__ encounters an |
|
|
2238 |
end-of-file the normal __yywrap()__ processing is done. A |
|
|
2239 |
``real'' end-of-file is returned by __input()__ as |
|
|
2240 |
''EOF.'' |
|
|
2241 |
|
|
|
2242 |
|
|
|
2243 |
Input is instead controlled by defining the __YY_INPUT__ |
|
|
2244 |
macro. |
|
|
2245 |
|
|
|
2246 |
|
|
|
2247 |
The ''flex'' restriction that __input()__ cannot be |
|
|
2248 |
redefined is in accordance with the POSIX specification, |
|
|
2249 |
which simply does not specify any way of controlling the |
|
|
2250 |
scanner's input other than by making an initial assignment |
|
|
2251 |
to ''yyin.'' |
|
|
2252 |
|
|
|
2253 |
|
|
|
2254 |
- |
|
|
2255 |
|
|
|
2256 |
|
|
|
2257 |
The __unput()__ routine is not redefinable. This |
|
|
2258 |
restriction is in accordance with POSIX. |
|
|
2259 |
|
|
|
2260 |
|
|
|
2261 |
- |
|
|
2262 |
|
|
|
2263 |
|
|
|
2264 |
''flex'' scanners are not as reentrant as ''lex'' |
|
|
2265 |
scanners. In particular, if you have an interactive scanner |
|
|
2266 |
and an interrupt handler which long-jumps out of the |
|
|
2267 |
scanner, and the scanner is subsequently called again, you |
|
|
2268 |
may get the following message: |
|
|
2269 |
|
|
|
2270 |
|
|
|
2271 |
fatal flex scanner internal error--end of buffer missed |
|
|
2272 |
To reenter the scanner, first use |
|
|
2273 |
|
|
|
2274 |
|
|
|
2275 |
yyrestart( yyin ); |
|
|
2276 |
Note that this call will throw away any buffered input; usually this isn't a problem with an interactive scanner. |
|
|
2277 |
|
|
|
2278 |
|
|
|
2279 |
Also note that flex C++ scanner classes ''are'' |
|
|
2280 |
reentrant, so if using C++ is an option for you, you should |
|
|
2281 |
use them instead. See |
|
|
2282 |
'' |
|
|
2283 |
|
|
|
2284 |
|
|
|
2285 |
- |
|
|
2286 |
|
|
|
2287 |
|
|
|
2288 |
__output()__ is not supported. Output from the |
|
|
2289 |
__ECHO__ macro is done to the file-pointer ''yyout'' |
|
|
2290 |
(default ''stdout).'' |
|
|
2291 |
|
|
|
2292 |
|
|
|
2293 |
__output()__ is not part of the POSIX |
|
|
2294 |
specification. |
|
|
2295 |
|
|
|
2296 |
|
|
|
2297 |
- |
|
|
2298 |
|
|
|
2299 |
|
|
|
2300 |
''lex'' does not support exclusive start conditions (%x), |
|
|
2301 |
though they are in the POSIX specification. |
|
|
2302 |
|
|
|
2303 |
|
|
|
2304 |
- |
|
|
2305 |
|
|
|
2306 |
|
|
|
2307 |
When definitions are expanded, ''flex'' encloses them in |
|
|
2308 |
parentheses. With lex, the following: |
|
|
2309 |
|
|
|
2310 |
|
|
|
2311 |
NAME [[A-Z][[A-Z0-9]* |
|
|
2312 |
%% |
|
|
2313 |
foo{NAME}? printf( |
|
|
2314 |
will not match the string flex,'' the rule will be expanded to '' |
|
|
2315 |
|
|
|
2316 |
|
|
|
2317 |
Note that if the definition begins with __^__ or ends |
|
|
2318 |
with __$__ then it is ''not'' expanded with |
|
|
2319 |
parentheses, to allow these operators to appear in |
|
|
2320 |
definitions without losing their special meanings. But the |
|
|
2321 |
____ and ____ |
|
|
2322 |
operators cannot be used in a ''flex'' |
|
|
2323 |
definition. |
|
|
2324 |
|
|
|
2325 |
|
|
|
2326 |
Using __-l__ results in the ''lex'' behavior of no |
|
|
2327 |
parentheses around the definition. |
|
|
2328 |
|
|
|
2329 |
|
|
|
2330 |
The POSIX specification is that the definition be enclosed |
|
|
2331 |
in parentheses. |
|
|
2332 |
|
|
|
2333 |
|
|
|
2334 |
- |
|
|
2335 |
|
|
|
2336 |
|
|
|
2337 |
Some implementations of ''lex'' allow a rule's action to |
|
|
2338 |
begin on a separate line, if the rule's pattern has trailing |
|
|
2339 |
whitespace: |
|
|
2340 |
|
|
|
2341 |
|
|
|
2342 |
%% |
|
|
2343 |
foo|bar |
|
|
2344 |
''flex'' does not support this feature. |
|
|
2345 |
|
|
|
2346 |
|
|
|
2347 |
- |
|
|
2348 |
|
|
|
2349 |
|
|
|
2350 |
The ''lex'' __%r__ (generate a Ratfor scanner) option |
|
|
2351 |
is not supported. It is not part of the POSIX |
|
|
2352 |
specification. |
|
|
2353 |
|
|
|
2354 |
|
|
|
2355 |
- |
|
|
2356 |
|
|
|
2357 |
|
|
|
2358 |
After a call to __unput(),__ ''yytext'' is undefined |
|
|
2359 |
until the next token is matched, unless the scanner was |
|
|
2360 |
built using __%array.__ This is not the case with |
|
|
2361 |
''lex'' or the POSIX specification. The __-l__ option |
|
|
2362 |
does away with this incompatibility. |
|
|
2363 |
|
|
|
2364 |
|
|
|
2365 |
- |
|
|
2366 |
|
|
|
2367 |
|
|
|
2368 |
The precedence of the __{}__ (numeric range) operator is |
|
|
2369 |
different. ''lex'' interprets |
|
|
2370 |
''flex'' interprets it as |
|
|
2371 |
'' |
|
|
2372 |
|
|
|
2373 |
|
|
|
2374 |
- |
|
|
2375 |
|
|
|
2376 |
|
|
|
2377 |
The precedence of the __^__ operator is different. |
|
|
2378 |
''lex'' interprets |
|
|
2379 |
''flex'' interprets it as |
|
|
2380 |
'' |
|
|
2381 |
|
|
|
2382 |
|
|
|
2383 |
- |
|
|
2384 |
|
|
|
2385 |
|
|
|
2386 |
The special table-size declarations such as __%a__ |
|
|
2387 |
supported by ''lex'' are not required by ''flex'' |
|
|
2388 |
scanners; ''flex'' ignores them. |
|
|
2389 |
|
|
|
2390 |
|
|
|
2391 |
- |
|
|
2392 |
|
|
|
2393 |
|
|
|
2394 |
The name FLEX_SCANNER is #define'd so scanners may be |
|
|
2395 |
written for use with either ''flex'' or ''lex.'' |
|
|
2396 |
Scanners also include __YY_FLEX_MAJOR_VERSION__ and |
|
|
2397 |
__YY_FLEX_MINOR_VERSION__ indicating which version of |
|
|
2398 |
''flex'' generated the scanner (for example, for the 2.5 |
|
|
2399 |
release, these defines would be 2 and 5 |
|
|
2400 |
respectively). |
|
|
2401 |
|
|
|
2402 |
|
|
|
2403 |
The following ''flex'' features are not included in |
|
|
2404 |
''lex'' or the POSIX specification: |
|
|
2405 |
|
|
|
2406 |
|
|
|
2407 |
C++ scanners |
|
|
2408 |
%option |
|
|
2409 |
start condition scopes |
|
|
2410 |
start condition stacks |
|
|
2411 |
interactive/non-interactive scanners |
|
|
2412 |
yy_scan_string() and friends |
|
|
2413 |
yyterminate() |
|
|
2414 |
yy_set_interactive() |
|
|
2415 |
yy_set_bol() |
|
|
2416 |
YY_AT_BOL() |
|
|
2417 |
plus almost all of the flex flags. The last feature in the list refers to the fact that with ''flex'' you can put multiple actions on the same line, separated with semi-colons, while with ''lex,'' the following |
|
|
2418 |
|
|
|
2419 |
|
|
|
2420 |
foo handle_foo(); ++num_foos_seen; |
|
|
2421 |
is (rather surprisingly) truncated to |
|
|
2422 |
|
|
|
2423 |
|
|
|
2424 |
foo handle_foo(); |
|
|
2425 |
''flex'' does not truncate the action. Actions that are not enclosed in braces are simply terminated at the end of the line. |
|
|
2426 |
!!DIAGNOSTICS |
|
|
2427 |
|
|
|
2428 |
|
|
|
2429 |
''warning, rule cannot be matched'' indicates that the |
|
|
2430 |
given rule cannot be matched because it follows other rules |
|
|
2431 |
that will always match the same text as it. For example, in |
|
|
2432 |
the following |
|
|
2433 |
'' |
|
|
2434 |
|
|
|
2435 |
|
|
|
2436 |
[[a-z]+ got_identifier(); |
|
|
2437 |
foo got_foo(); |
|
|
2438 |
Using __REJECT__ in a scanner suppresses this warning. |
|
|
2439 |
|
|
|
2440 |
|
|
|
2441 |
''warning,'' __-s__ ''option given but default rule |
|
|
2442 |
can be matched'' means that it is possible (perhaps only |
|
|
2443 |
in a particular start condition) that the default rule |
|
|
2444 |
(match any single character) is the only one that will match |
|
|
2445 |
a particular input. Since __-s__ was given, presumably |
|
|
2446 |
this is not intended. |
|
|
2447 |
|
|
|
2448 |
|
|
|
2449 |
''reject_used_but_not_detected undefined'' or |
|
|
2450 |
''yymore_used_but_not_detected undefined -'' These errors |
|
|
2451 |
can occur at compile time. They indicate that the scanner |
|
|
2452 |
uses __REJECT__ or __yymore()__ but that ''flex'' |
|
|
2453 |
failed to notice the fact, meaning that ''flex'' scanned |
|
|
2454 |
the first two sections looking for occurrences of these |
|
|
2455 |
actions and failed to find any, but somehow you snuck some |
|
|
2456 |
in (via a #include file, for example). Use __%option |
|
|
2457 |
reject__ or __%option yymore__ to indicate to flex that |
|
|
2458 |
you really do use these features. |
|
|
2459 |
|
|
|
2460 |
|
|
|
2461 |
''flex scanner jammed -'' a scanner compiled with |
|
|
2462 |
__-s__ has encountered an input string which wasn't |
|
|
2463 |
matched by any of its rules. This error can also occur due |
|
|
2464 |
to internal problems. |
|
|
2465 |
|
|
|
2466 |
|
|
|
2467 |
''token too large, exceeds YYLMAX -'' your scanner uses |
|
|
2468 |
__%array__ and one of its rules matched a string longer |
|
|
2469 |
than the __YYLMAX__ constant (8K bytes by default). You |
|
|
2470 |
can increase the value by #define'ing __YYLMAX__ in the |
|
|
2471 |
definitions section of your ''flex'' input. |
|
|
2472 |
|
|
|
2473 |
|
|
|
2474 |
''scanner requires -8 flag to use the character 'x' -'' |
|
|
2475 |
Your scanner specification includes recognizing the 8-bit |
|
|
2476 |
character '''x''' and you did not specify the -8 flag, |
|
|
2477 |
and your scanner defaulted to 7-bit because you used the |
|
|
2478 |
__-Cf__ or __-CF__ table compression options. See the |
|
|
2479 |
discussion of the __-7__ flag for details. |
|
|
2480 |
|
|
|
2481 |
|
|
|
2482 |
''flex scanner push-back overflow -'' you used |
|
|
2483 |
__unput()__ to push back so much text that the scanner's |
|
|
2484 |
buffer could not hold both the pushed-back text and the |
|
|
2485 |
current token in __yytext.__ Ideally the scanner should |
|
|
2486 |
dynamically resize the buffer in this case, but at present |
|
|
2487 |
it does not. |
|
|
2488 |
|
|
|
2489 |
|
|
|
2490 |
''input buffer overflow, can't enlarge buffer because |
|
|
2491 |
scanner uses REJECT -'' the scanner was working on |
|
|
2492 |
matching an extremely large token and needed to expand the |
|
|
2493 |
input buffer. This doesn't work with scanners that use |
|
|
2494 |
__REJECT.__ |
|
|
2495 |
|
|
|
2496 |
|
|
|
2497 |
''fatal flex scanner internal error--end of buffer missed |
|
|
2498 |
-'' This can occur in an scanner which is reentered after |
|
|
2499 |
a long-jump has jumped out (or over) the scanner's |
|
|
2500 |
activation frame. Before reentering the scanner, |
|
|
2501 |
use: |
|
|
2502 |
|
|
|
2503 |
|
|
|
2504 |
yyrestart( yyin ); |
|
|
2505 |
or, as noted above, switch to using the C++ scanner class. |
|
|
2506 |
|
|
|
2507 |
|
|
|
2508 |
''too many start conditions in '' |
|
|
2509 |
you listed more start conditions in a |
|
|
2510 |
'' |
|
|
2511 |
!!FILES |
|
|
2512 |
|
|
|
2513 |
|
|
|
2514 |
__-lfl__ |
|
|
2515 |
|
|
|
2516 |
|
|
|
2517 |
library with which scanners must be linked. |
|
|
2518 |
|
|
|
2519 |
|
|
|
2520 |
''lex.yy.c'' |
|
|
2521 |
|
|
|
2522 |
|
|
|
2523 |
generated scanner (called ''lexyy.c'' on some |
|
|
2524 |
systems). |
|
|
2525 |
|
|
|
2526 |
|
|
|
2527 |
''lex.yy.cc'' |
|
|
2528 |
|
|
|
2529 |
|
|
|
2530 |
generated C++ scanner class, when using |
|
|
2531 |
__-+.__ |
|
|
2532 |
|
|
|
2533 |
|
|
|
2534 |
'''' |
|
|
2535 |
|
|
|
2536 |
|
|
|
2537 |
header file defining the C++ scanner base class, |
2 |
perry |
2538 |
__!FlexLexer,__ and its derived class, |
1 |
perry |
2539 |
__yyFlexLexer.__ |
|
|
2540 |
|
|
|
2541 |
|
|
|
2542 |
''flex.skl'' |
|
|
2543 |
|
|
|
2544 |
|
|
|
2545 |
skeleton scanner. This file is only used when building flex, |
|
|
2546 |
not when flex executes. |
|
|
2547 |
|
|
|
2548 |
|
|
|
2549 |
''lex.backup'' |
|
|
2550 |
|
|
|
2551 |
|
|
|
2552 |
backing-up information for __-b__ flag (called |
|
|
2553 |
''lex.bck'' on some systems). |
|
|
2554 |
!!DEFICIENCIES / BUGS |
|
|
2555 |
|
|
|
2556 |
|
|
|
2557 |
Some trailing context patterns cannot be properly matched |
|
|
2558 |
and generate warning messages ( |
|
|
2559 |
|
|
|
2560 |
|
|
|
2561 |
For some trailing context rules, parts which are actually |
|
|
2562 |
fixed-length are not recognized as such, leading to the |
|
|
2563 |
abovementioned performance loss. In particular, parts using |
|
|
2564 |
'|' or {n} (such as |
|
|
2565 |
|
|
|
2566 |
|
|
|
2567 |
Combining trailing context with the special '|' action can |
|
|
2568 |
result in ''fixed'' trailing context being turned into |
|
|
2569 |
the more expensive ''variable'' trailing context. For |
|
|
2570 |
example, in the following: |
|
|
2571 |
|
|
|
2572 |
|
|
|
2573 |
%% |
|
|
2574 |
abc | |
|
|
2575 |
xyz/def |
|
|
2576 |
Use of __unput()__ invalidates yytext and yyleng, unless the __%array__ directive or the __-l__ option has been used. |
|
|
2577 |
|
|
|
2578 |
|
|
|
2579 |
Pattern-matching of NUL's is substantially slower than |
|
|
2580 |
matching other characters. |
|
|
2581 |
|
|
|
2582 |
|
|
|
2583 |
Dynamic resizing of the input buffer is slow, as it entails |
|
|
2584 |
rescanning all the text matched so far by the current |
|
|
2585 |
(generally huge) token. |
|
|
2586 |
|
|
|
2587 |
|
|
|
2588 |
Due to both buffering of input and read-ahead, you cannot |
|
|
2589 |
intermix calls to |
|
|
2590 |
getchar(),__ with ''flex'' rules and expect |
|
|
2591 |
it to work. Call __input()__ instead. |
|
|
2592 |
|
|
|
2593 |
|
|
|
2594 |
The total table entries listed by the __-v__ flag |
|
|
2595 |
excludes the number of table entries needed to determine |
|
|
2596 |
what rule has been matched. The number of entries is equal |
|
|
2597 |
to the number of DFA states if the scanner does not use |
|
|
2598 |
__REJECT,__ and somewhat greater than the number of |
|
|
2599 |
states if it does. |
|
|
2600 |
|
|
|
2601 |
|
|
|
2602 |
__REJECT__ cannot be used with the __-f__ or __-F__ |
|
|
2603 |
options. |
|
|
2604 |
|
|
|
2605 |
|
|
|
2606 |
The ''flex'' internal algorithms need |
|
|
2607 |
documentation. |
|
|
2608 |
!!SEE ALSO |
|
|
2609 |
|
|
|
2610 |
|
|
|
2611 |
lex(1), yacc(1), sed(1), awk(1). |
|
|
2612 |
|
|
|
2613 |
|
|
|
2614 |
John Levine, Tony Mason, and Doug Brown, ''Lex |
|
|
2615 |
'' O'Reilly and Associates. Be sure to get the 2nd |
|
|
2616 |
edition. |
|
|
2617 |
|
|
|
2618 |
|
|
|
2619 |
M. E. Lesk and E. Schmidt, ''LEX - Lexical Analyzer |
|
|
2620 |
Generator'' |
|
|
2621 |
|
|
|
2622 |
|
|
|
2623 |
Alfred Aho, Ravi Sethi and Jeffrey Ullman, ''Compilers: |
|
|
2624 |
Principles, Techniques and Tools,'' Addison-Wesley (1986). |
|
|
2625 |
Describes the pattern-matching techniques used by |
|
|
2626 |
''flex'' (deterministic finite automata). |
|
|
2627 |
!!AUTHOR |
|
|
2628 |
|
|
|
2629 |
|
|
|
2630 |
Vern Paxson, with the help of many ideas and much |
|
|
2631 |
inspiration from Van Jacobson. Original version by Jef |
|
|
2632 |
Poskanzer. The fast table representation is a partial |
|
|
2633 |
implementation of a design done by Van Jacobson. The |
|
|
2634 |
implementation was done by Kevin Gong and Vern |
|
|
2635 |
Paxson. |
|
|
2636 |
|
|
|
2637 |
|
|
|
2638 |
Thanks to the many ''flex'' beta-testers, feedbackers, |
|
|
2639 |
and contributors, especially Francois Pinard, Casey Leedom, |
|
|
2640 |
Robert Abramovitz, Stan Adermann, Terry Allen, David |
|
|
2641 |
Barker-Plummer, John Basrai, Neal Becker, Nelson H.F. Beebe, |
|
|
2642 |
benson@odi.com, Karl Berry, Peter A. Bigot, Simon Blanchard, |
|
|
2643 |
Keith Bostic, Frederic Brehm, Ian Brockbank, Kin Cho, Nick |
|
|
2644 |
Christopher, Brian Clapper, J.T. Conklin, Jason Coughlin, |
|
|
2645 |
Bill Cox, Nick Cropper, Dave Curtis, Scott David Daniels, |
|
|
2646 |
Chris G. Demetriou, Theo Deraadt, Mike Donahue, Chuck |
|
|
2647 |
Doucette, Tom Epperly, Leo Eskin, Chris Faylor, Chris |
|
|
2648 |
Flatters, Jon Forrest, Jeffrey Friedl, Joe Gayda, Kaveh R. |
|
|
2649 |
Ghazi, Wolfgang Glunz, Eric Goldman, Christopher M. Gould, |
|
|
2650 |
Ulrich Grepel, Peer Griebel, Jan Hajic, Charles Hemphill, |
|
|
2651 |
NORO Hideo, Jarkko Hietaniemi, Scott Hofmann, Jeff Honig, |
|
|
2652 |
Dana Hudes, Eric Hughes, John Interrante, Ceriel Jacobs, |
|
|
2653 |
Michal Jaegermann, Sakari Jalovaara, Jeffrey R. Jones, Henry |
|
|
2654 |
Juengst, Klaus Kaempf, Jonathan I. Kamens, Terrence O Kane, |
|
|
2655 |
Amir Katz, ken@ken.hilco.com, Kevin B. Kenny, Steve Kirsch, |
|
|
2656 |
Winfried Koenig, Marq Kole, Ronald Lamprecht, Greg Lee, |
|
|
2657 |
Rohan Lenard, Craig Leres, John Levine, Steve Liddle, David |
|
|
2658 |
Loffredo, Mike Long, Mohamed el Lozy, Brian Madsen, Malte, |
|
|
2659 |
Joe Marshall, Bengt Martensson, Chris Metcalf, Luke Mewburn, |
|
|
2660 |
Jim Meyering, R. Alexander Milowski, Erik Naggum, G.T. |
|
|
2661 |
Nicol, Landon Noll, James Nordby, Marc Nozell, Richard |
|
|
2662 |
Ohnemus, Karsten Pahnke, Sven Panne, Roland Pesch, Walter |
|
|
2663 |
Pelissero, Gaumond Pierre, Esmond Pitt, Jef Poskanzer, Joe |
|
|
2664 |
Rahmeh, Jarmo Raiha, Frederic Raimbault, Pat Rankin, Rick |
|
|
2665 |
Richardson, Kevin Rodgers, Kai Uwe Rommel, Jim Roskind, |
|
|
2666 |
Alberto Santini, Andreas Scherer, Darrell Schiebel, Raf |
|
|
2667 |
Schietekat, Doug Schmidt, Philippe Schnoebelen, Andreas |
|
|
2668 |
Schwab, Larry Schwimmer, Alex Siegel, Eckehard Stolz, |
|
|
2669 |
Jan-Erik Strvmquist, Mike Stump, Paul Stuart, Dave Tallman, |
|
|
2670 |
Ian Lance Taylor, Chris Thewalt, Richard M. Timoney, Jodi |
|
|
2671 |
Tsai, Paul Tuinenga, Gary Weik, Frank Whaley, Gerhard |
|
|
2672 |
Wilhelms, Kent Williams, Ken Yap, Ron Zellar, Nathan Zelle, |
|
|
2673 |
David Zuhn, and those whose names have slipped my marginal |
|
|
2674 |
mail-archiving skills but whose contributions are |
|
|
2675 |
appreciated all the same. |
|
|
2676 |
|
|
|
2677 |
|
|
|
2678 |
Thanks to Keith Bostic, Jon Forrest, Noah Friedman, John |
|
|
2679 |
Gilmore, Craig Leres, John Levine, Bob Mulcahy, G.T. Nicol, |
|
|
2680 |
Francois Pinard, Rich Salz, and Richard Stallman for help |
|
|
2681 |
with various distribution headaches. |
|
|
2682 |
|
|
|
2683 |
|
|
|
2684 |
Thanks to Esmond Pitt and Earle Horton for 8-bit character |
|
|
2685 |
support; to Benson Margulies and Fred Burke for C++ support; |
|
|
2686 |
to Kent Williams and Tom Epperly for C++ class support; to |
|
|
2687 |
Ove Ewerlid for support of NUL's; and to Eric Hughes for |
|
|
2688 |
support of multiple buffers. |
|
|
2689 |
|
|
|
2690 |
|
|
|
2691 |
This work was primarily done when I was with the Real Time |
|
|
2692 |
Systems Group at the Lawrence Berkeley Laboratory in |
|
|
2693 |
Berkeley, CA. Many thanks to all there for the support I |
|
|
2694 |
received. |
|
|
2695 |
|
|
|
2696 |
|
|
|
2697 |
Send comments to vern@ee.lbl.gov. |
|
|
2698 |
---- |