Difference between revisions of "PreludeTour"
From HaskellWiki
Line 1:  Line 1:  
−  = 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 