PreludeTour
From HaskellWiki
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:  Applied 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 