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99 questions/Solutions/4

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(correction (foldl) and shortened version of foldr)
m
Line 11: Line 11:
 
myLength'' = foldr (\_ n -> n + 1) 0
 
myLength'' = foldr (\_ n -> n + 1) 0
 
myLength''' = foldr (\_ -> (+1)) 0
 
myLength''' = foldr (\_ -> (+1)) 0
  +
</haskell>
  +
  +
<haskell>
  +
myLength' xs = snd $ last $ zip xs [1..] -- Just for fun
 
</haskell>
 
</haskell>
   

Revision as of 22:46, 1 December 2010

(*) Find the number of elements of a list.

myLength           :: [a] -> Int
myLength []        =  0
myLength (_:xs)    =  1 + myLength xs
myLength'   =  foldl (\n _ -> n + 1) 0
myLength''  =  foldr (\_ n -> n + 1) 0
myLength''' =  foldr (\_ -> (+1)) 0
myLength' xs = snd $ last $ zip xs [1..] -- Just for fun
This is
length
in
Prelude
.