PreludeTour: Difference between revisions

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= A Tour of the Haskell Prelude =
== A Tour of the Haskell Prelude ==
 
 
;'''abs''':
{| border="0" cellpadding="4"
|-
| ''type:'' || <hask>abs :: Num a => a -> a</hask>
|-
| ''description:'' || returns the absolute value of a number.
|-
| ''definition:''
| <haskell>
abs x
  | x >= 0 = x
  | otherwise = -x
</haskell>
|-
| ''usage:''
| <pre>
Prelude> abs (-3)
3
</pre>
|}
 
;'''all''':
{| border="0" cellpadding="4"
|-
| ''type:'' || <hask>all :: (a -> Bool) -> [a] -> Bool</hask>
|-
| ''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:''
| <haskell>
all p xs = and (map p xs)
</haskell>
|-
| ''usage:''
| <pre>
Prelude> all (<11) [1..10]
True
Prelude> all isDigit "123abc"
False
</pre>
|}

Revision as of 13:21, 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