Difference between revisions of "PreludeTour"

From HaskellWiki
Jump to: navigation, search
m (Reverted edits by Tomjaguarpaw (talk) to last revision by Bjpop)
 
(7 intermediate revisions by 2 users not shown)
Line 1: Line 1:
= A Tour of the Haskell Prelude =
+
== A Tour of the Haskell Prelude ==
 +
 
 +
 
 +
;<span id="abs">'''abs'''</span>:
 +
{| 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>
 +
|}
 +
 
 +
;<span id="all">'''all'''</span>:
 +
{| border="0" cellpadding="4"
 +
|-
 +
| ''type:'' || <hask>all :: (a -> Bool) -> [a] -> Bool</hask>
 +
|-
 +
| ''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:''
 +
| <haskell>
 +
all p xs = and (map p xs)
 +
</haskell>
 +
|-
 +
| ''usage:''
 +
| <pre>
 +
Prelude> all (<11) [1..10]
 +
True
 +
Prelude> all isDigit "123abc"
 +
False
 +
</pre>
 +
|}

Latest revision as of 15:19, 6 February 2021

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