Difference between revisions of "PreludeTour"

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Revision as of 13:30, 26 October 2009

A Tour of the Haskell Prelude

abs

type: abs :: Num a => a -> a
description: returns the absolute value of a number.
definition:
abs x
  | x >= 0 = x
  | otherwise = -x
usage:
Prelude> abs (-3)
3

all

type: all :: (a -> Bool) -> [a] -> Bool
description: pplied to a predicate and a list, returns True if all elements of the list satisfy the predicate, and False otherwise. Similar to the function any.
definition:
all p xs = and (map p xs)
usage:
Prelude> all (<11) [1..10]
True
Prelude> all isDigit "123abc"
False