Difference between revisions of "99 questions/Solutions/1"
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(Copied solution from 99 questions/1 to 10) |
(Added base case to myLast) |
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<haskell> |
<haskell> |
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myLast :: [a] -> a |
myLast :: [a] -> a |
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| + | myLast [] = error "No end for empty lists!" |
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myLast [x] = x |
myLast [x] = x |
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myLast (_:xs) = myLast xs |
myLast (_:xs) = myLast xs |
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myLast' = foldr1 (const id) |
myLast' = foldr1 (const id) |
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| + | -- Prelude> const 1 2 |
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| ⚫ | |||
| + | -- 1 |
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| + | -- Prelude> (flip const) 1 2 |
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| + | -- 2 |
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| + | myLast'' = foldr1 (flip const) |
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| + | |||
| ⚫ | |||
| + | |||
| + | myLast'''' = foldl1 (curry snd) |
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| + | |||
| + | myLast''''' [] = error "No end for empty lists!" |
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| + | myLast''''' x = x !! (length x -1) |
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| + | |||
</haskell> |
</haskell> |
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The <hask>Prelude</hask> also provides the function <hask>last</hask>. |
The <hask>Prelude</hask> also provides the function <hask>last</hask>. |
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| + | [[Category:Programming exercise spoilers]] |
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Latest revision as of 13:52, 25 August 2014
(*) Find the last element of a list.
myLast :: [a] -> a
myLast [] = error "No end for empty lists!"
myLast [x] = x
myLast (_:xs) = myLast xs
myLast' = foldr1 (const id)
-- Prelude> const 1 2
-- 1
-- Prelude> (flip const) 1 2
-- 2
myLast'' = foldr1 (flip const)
myLast''' = head . reverse
myLast'''' = foldl1 (curry snd)
myLast''''' [] = error "No end for empty lists!"
myLast''''' x = x !! (length x -1)
The Prelude also provides the function last.