Search results
Results From The WOW.Com Content Network
Here, the list [0..] represents , x^2>3 represents the predicate, and 2*x represents the output expression.. List comprehensions give results in a defined order (unlike the members of sets); and list comprehensions may generate the members of a list in order, rather than produce the entirety of the list thus allowing, for example, the previous Haskell definition of the members of an infinite list.
List comprehension is a syntactic construct available in some programming languages for creating a list based on existing lists. It follows the form of the mathematical set-builder notation (set comprehension) as distinct from the use of map and filter functions.
The same function, written using Glasgow Haskell Compiler's parallel list comprehension syntax (GHC extensions must be enabled using a special command-line flag, here -XParallelListComp, or by starting the source file with {-# LANGUAGE ParallelListComp #-}):
Haskell features lazy evaluation, lambda expressions, pattern matching, list comprehension, type classes and type polymorphism. It is a purely functional programming language, which means that functions generally have no side effects .
Haskell replaces the set-builder's braces with square brackets and uses symbols, including the standard set-builder vertical bar. The same can be achieved in Scala using Sequence Comprehensions, where the "for" keyword returns a list of the yielded variables using the "yield" keyword.
Or, via list comprehension: [x for x in list if pred(x)]. In Python 3, filter was changed to return an iterator rather than a list. [ 13 ] The complementary functionality, returning an iterator over elements for which the predicate is false, is also available in the standard library as filterfalse in the itertools module.
Gofer (Good for equational reasoning) is an implementation of the programming language Haskell intended for educational purposes and supporting a language based on version 1.2 of the Haskell report. It was replaced by Hugs. [1] Its syntax is closer to the earlier commercial language Miranda than the subsequently
In languages which support first-class functions and currying, map may be partially applied to lift a function that works on only one value to an element-wise equivalent that works on an entire container; for example, map square is a Haskell function which squares each element of a list.