99 questions/Solutions/2: Difference between revisions
< 99 questions | Solutions
(Add foldl based solution.) |
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myButLast'''' = head . tail . reverse | myButLast'''' = head . tail . reverse | ||
myButLast''''' = snd.(foldl (\(a,b) c -> (c,a)) (e1, e2)) | |||
where e1 = error "List too small!" | |||
e2 = error "List is null!" | |||
</haskell> | </haskell> | ||
[[Category:Programming exercise spoilers]] | [[Category:Programming exercise spoilers]] | ||
Revision as of 00:12, 11 May 2014
(*) Find the last but one element of a list.
myButLast :: [a] -> a
myButLast = last . init
myButLast' x = reverse x !! 1
myButLast'' [x,_] = x
myButLast'' (_:xs) = myButLast'' xs
myButLast''' (x:(_:[])) = x
myButLast''' (_:xs) = myButLast''' xs
myButLast'''' = head . tail . reverse
myButLast''''' = snd.(foldl (\(a,b) c -> (c,a)) (e1, e2))
where e1 = error "List too small!"
e2 = error "List is null!"