Differences between current version and predecessor to the previous major change of ML.
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| Newer page: | version 25 | Last edited on Tuesday, November 9, 2004 1:13:56 am | by AristotlePagaltzis | |
| Older page: | version 18 | Last edited on Monday, February 24, 2003 4:42:52 pm | by GlynWebster | Revert |
@@ -1,133 +1,36 @@
-''(I'm still working on this, so some parts will still be gibberish. --GlynWebster)'' %%%
-''(And I may be wandering off into little tutorials where I don't need to. What do you think? --GlynWebster)''%%%
-''(Tutorial'
s are good
, this is supposed to be an interesting place to go and learn stuff from
, however
, not all these concepts are exclusively
ML,
for instance StaticallyTyped
, HigherOrder, PolyMorphic, Functional, StandardisedLanguage
, are all attributes
of other programming languages too
, breaking these out into their own pages would be educational no?
-- PerryLorier)''
+__ML__ is a family of StaticallyTyped functional ProgrammingLanguage~
s with StrictEvaluation
, PolymorphicTypes
, HigherOrderFunctions
, a higher-order module system. [
ML] can be used interactively
for learning
, experimentation and testing
, or it can be compiled. The two major dialects of [ML]
are [OCaml] and [SML]. [SML] is a standardised language with several implementations. [OCaml] has a single OpenSource implementation, it extends [ML] with an [OOP] system. Both major dialects have compilers that produce native code that rival the speed
of [C++]
, and extensive standard and third
-party libraries.
-!!!ML
in one paragraph, with buzzwords
:
+[Why YOU want to program
in ML | http
://www.schizomaniac.net/ml.html] gives you a tour of the features of [ML] that make it a good general-purpose programming language. It talks about [SML], but what it says applies to [OCaml] as well.
-ML is a family
of StaticallyTyped
[1] [FunctionalLanguage]s with StrictEvaluation[4], PolyMorpicTypes, HigherOrderFunctions, a higher-order module system[5].
ML is very good general purpose programming language[6
] with a strength in pattern matching[7]. ML can be used interactively for learning, experimentation and testing, or it can be compiled. The two major dialects of ML are [Ocaml] and [SML]. SML is a standardised language[8] with several implementations[9]. Ocaml has a single open source implementation[10], it extends ML with an OOP system[11]. Both major dialects have compilers that produce native
code that rivals the speed of C++, and extensive standard[12] and third-party[13] libraries.
+!!!An example
of [ML] code:
-''
(Click
a footnote for more info
.)''
+<pre>
+__fun__ interpret_functionally
(program : opcode list) : unit =
+ (* Interprets
a parsed [Brainf*ck] program using integers
+ on a strip of TuringMachine tape as the memory
. *)
+ __let__
+ __val__ fresh_tape = Tape.make()
+ __fun__ step (tape, op) =
+ __let__ byte = Tape.read(tape) __in__
+ __case__ op __of__
+ Inc_ptr n => times(n, Tape.forward, tape)
+ | Dec_ptr n => times(n, Tape.back, tape)
+ | Inc_byte n => Tape.write(byte + n, tape)
+ | Dec_byte n => Tape.write(byte - n, tape)
+ | Putchar => ( putchar(byte) ; tape )
+ | Getchar => Tape.write(getchar(), tape)
+ | Loop body =>
+ __if__ byte = 0 __then__ tape
+ __else__ step (step_sequence (tape, body), op)
+ __end__
+ __fun__ step_sequence (tape, oplist) =
+ List.foldl(step, tape, oplist)
+ __in__
+ ignore (step_sequence(fresh_tape, program)
)
+ __end__
+</pre>
-!!!An example of ML code:
-
- __fun__ interpret_functionally (program : opcode list) : unit =
- (* Interprets a parsed [Brainf*ck] program using integers
- on a strip of TuringMachine tape as the memory. *)
- __let__
- __val__ fresh_tape = Tape.make()
- __fun__ step (tape, op) =
- __let__ byte = Tape.read(tape) __in__
- __case__ op __of__
- Inc_ptr n => times(n, Tape.forward, tape)
- | Dec_ptr n => times(n, Tape.back, tape)
- | Inc_byte n => Tape.write(byte + n, tape)
- | Dec_byte n => Tape.write(byte - n, tape)
- | Putchar => ( putchar(byte) ; tape )
- | Getchar => Tape.write(getchar(), tape)
- | Loop body =>
- __if__ byte = 0 __then__ tape
- __else__ step (step_sequence (tape, body), op)
- __end__
- __fun__ step_sequence (tape, oplist) =
- List.foldl(step, tape, oplist)
- __in__
- ignore (step_sequence(fresh_tape, program))
- __end__
-
-. The following examples will be in Ocaml
.)
+(This is in [
SML]
.)
----
-
-[1] ML can determine a variable's type by analyzing how it is used: you only need to declare types in places where you think it improves your code's clarity.
-
-[4] ML uses StrictEvaluation. This means that ML can allow reassignable variables and a conventional I/O system -- and it does.
-
-''[Haskell]'s main semantic difference from ML is that is it uses LazyEvaluation. If you enjoyed Haskell programming at WaikatoUniversity but because exasperated with [Monad]s and working out convoluted ways to make your programs preserve state
, ML may be the thing for you.''
-
-
-[5] The __Higher-Order Module System__.
-
-Modules are used to group related types, functions and classes, and to hide implementation details. The customary way to define a type in ML is to wrap it in a module with all the functions that operate on it. Optionally you can hide the definition of the type to make the module into an [AbstractDataType].
-
-Some modules in Ocaml's standard library just define groups of related functions, such as [Unix | http://caml.inria.fr/ocaml/htmlman/libref/Unix.html ], and some define abstract data types, such as [Hashtbl | http://caml.inria.fr/ocaml/htmlman/libref/Hashtbl.html].
-
-ML's equivalent of [C++]'s templates is the ''functor'', an ML module that takes another module as a parameter and uses the definitions in it to create a more specialised module. (You don't really need to understand these to make good use of ML.)
-
-An example: [Set.Make | http://caml.inria.fr/ocaml/htmlman/libref/Set.Make.html] is a functor that takes any module that contains these definitions:
-
- __type__ t ''(* any type at all *)''
- __val__ compare : t -> t -> int ''(* compares t's like strcmp does strings *)''
-
-and creates an abstract data type module for sets of type ''t''. [String | http://caml.inria.fr/ocaml/htmlman/libref/String.html] contains the
-necessary definitions (t = string) so we can use that:
-
- # __module__ !StringSet = Set.Make(String);;
- ''module !StringSet :''
- ''sig''
- ''type elt = string''
- ''and t''
- ''val empty : t''
- ''val is_empty : t -> bool''
- ''val mem : elt -> t -> bool''
- ''val add : elt -> t -> t''
- ...etc...
- ''end''
-
-This example doesn't do anything that can't be done with polymorphic types, but the idea is that you can replace any group types, functions or classes in a module this way.
-
-[6] __ML is very good general purpose programming language.__
-
-The type system means that even when I just sit down and hack, I get good quality code.
-
-* I can leave out type definitions. This lets me program in the succinct, flexible way I can in [Python], without the let-down of having all my type errors pop up a runtime.
-
-* The type system is very expressive. It encourages a style of programming where I think about my data, what it consists of and how I will transform it. Programs designed by type tend to be very modular -- they almost have to be by definition.
-
-* The type system is very exact. It allows the compiler to spot many big, logical errors at compile time, and well as the little nit-picky syntactic ones.
-
-''(more to say..)''
-
-
-[7] __Pattern matching__ is ML's strength. ML has an expression that is halfway between [C]'s__switch__ and declaration statements. In SML it is called __case__ and in Ocaml it is called __match__. Instead matching a value with single constants, like the __switch__ statement, __match__ can match values of any complexity by example, and select parts of the value to assign to variables as it does it.
-
-__Match__ statements are very clear and compact.
-
-''(example to come...)''
-
-Pattern matching is a very useful in general, but it is particularly handy in programs that manipulate complex tree-structured data, such as the parse trees in compilers. The [original ML language| http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?ML] was designed by someone who needed to do a ''lot'' of automated algebra on statements of symbolic logic.
-
-[8] __The SML standard.__ The language and standard library of SML are formally defined in the book [Definition of Standard ML| http://mitpress.mit.edu/catalog/item/default.asp?ttype=2&tid=3874]. (This is unusually thorough.)
-
-There is a copy at the WaikatoUniversity library.
-
-[9] __SML Implementations:__
-
-[Standard ML of New Jersey | http://cm.bell-labs.com/cm/cs/what/smlnj/] is the biggy. ''(can any one else describe it? I've not used it.)''
-
-[Moscow SML | http://www.dina.dk/~sestoft/mosml.html ] is a smaller, ByteCode interpreted SML that might be a better choice if you want to quickly download something to experiment with.
-
-
-[10] __The Ocaml Implementation__
-
-There is a single OpenSource implementation of [Ocaml]. A large community of users who don't want their code broken pressure the Ocaml development team to keep new versions standard or backwards compatible. [Python] and [Perl] are developed the same way. This
-approach works well once the community user is large enough. Ocaml's user community has been the necessary size for many years.
-
-An interpreter for the older [Caml Light | http://caml.inria.fr/overview-caml-light-eng.html] language is still available because it can be made to work on small computers, e.g. 286 PCs. It is an subset of Objective Caml, so there is little other reason to use it.
-
-
-[11] One of Ocaml's extentions to the original ML language is an ObjectOrientedProgramming system. Ocaml's OOP has everything you'd expect after using [Java] or [C++]. The syntax is quite different; class declarations are much more compact.
-
-A big improvement is that container classes are [polymorphic | PolymorphicTypes]. In C++ and Java container objects only recognise objects inside themselves as being members of the __Object__ class. You have to cast objects back the appropriate class when you remove them from the container. In Ocaml, if you want a container object to specifically contain objects that are of the class __fruitbat__, you can say so.
-
-See [Objects in Caml | http://pauillac.inria.fr/ocaml/htmlman/manual005.html]
-
-[12] __Standard Libraries.__
-
-The [SML Basis Library | http://cm.bell-labs.com/cm/cs/what/smlnj/doc/basis/pages/sml-std-basis.html] is said to be very well designed. %%%
-''The Basis library is indeed very well designed, but for SML/NJ (one of the major SML compilers) it is poorly documented, making it somewhat difficult to use. --GianPerrone'' %%%
-''The Basis Library pages I've linked to above seem adequate to me. Or those not what you are talking about? --GlynWebster''
-
-Ocaml's library is divided into: a [core library |http://caml.inria.fr/ocaml/htmlman/manual033.html], types and function available at all times; an implementation independent [standard library | http://caml.inria.fr/ocaml/htmlman/manual034.html], modules that can be imported; and set of [optional libraries | http://caml.inria.fr/ocaml/htmlman/index.html#p:library] that are either implementation dependent or special purpose.
-
-
-[13] __Ocaml Third-Party Libraries:__ [The Caml Link Database | http://www.npc.de/ocaml/linkdb/] and [The Hump | http://caml.inria.fr/humps/index.html] are the central repositories for [Ocaml] software.
+CategoryProgrammingLanguages
, CategoryFunctionalProgrammingLanguages
