Difference between revisions of "PreludeTour"
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Tomjaguarpaw (talk  contribs) (Tour was cut short for some reason) 
m (Reverted edits by Tomjaguarpaw (talk) to last revision by Bjpop) 

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+  == 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 