Difference between revisions of "PreludeTour"
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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 