PreludeTour

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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