Differences between version 5 and revision by previous author of LazyEvaluation.
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| Newer page: | version 5 | Last edited on Sunday, March 7, 2004 9:34:34 am | by AristotlePagaltzis | Revert |
| Older page: | version 2 | Last edited on Sunday, February 16, 2003 5:31:15 pm | by GlynWebster | Revert |
@@ -1,8 +1,5 @@
+LazyEvaluation is an approach that a ProgrammingLanguage can take to evaluating expressions. With LazyEvaluation a function is passed whole expressions as arguments, and does not evaluate them until it needs their values.
-''Lazy evaluation'' is an approach that a ProgrammingLanguage can take to evaluating expressions. With ''
lazy evaluation'' a function is passed whole expressions as arguments, and does
not evaluate them until it needs
their values
. (I won
't go into __why__ you'd want
that, but there are good reasons
.)
+You could call [C]
's __&&__ and __||__ operators
lazy operators: they do
not always
evaluate their second arguments
. But this is a built-in feature of [C] and there
's no way to specify user defined operators
that work that way. In [Haskell] f.ex
, which is the most widely used lazy functional programming language, you can
.
-[Haskell] is the most widely used lazy FunctionalLanguage.
-
-You could call [C]'s __&&__ and __||__ operators lazy operators. They do not always evaluate their second arguments. This is is built-in feature of C though, you cannot define your own operators that work that way. In Haskell you can.
-
-. Programmers needs to provide some way to keep I/O operations in the correct sequence
. Lazy languages don't assume a linear flow of time: you have to model that explicitly in your programs! Haskell uses
a data structure called the [Monad] to control sequential operations
.
+I/O is problematic in lazy languages. Lazy languages don't assume a linear flow of time: you have to model that explicitly in your programs! Programmers need to provide some way to keep I/O operations in the correct sequence; in [
Haskell] this is done using
a data structure called the "monad"
.
