Difference between revisions of "Implicit parameters"
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m (Fix link to GHC doc) |
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| − | + | {{GHCUsersGuide|https://downloads.haskell.org/~ghc/latest/docs/html/users_guide/glasgow_exts.html#implicit-parameters Implicit Parameters section}} |
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Working example: |
Working example: |
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import Data.List (sortBy) |
import Data.List (sortBy) |
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| − | + | sortBy' :: (?cmp :: a -> a -> Ordering) => [a] -> [a] |
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| − | + | sortBy' = sortBy ?cmp |
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| + | |||
| + | sort :: Ord a => [a] -> [a] |
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| + | sort = let ?cmp = compare in sortBy' |
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| − | main = |
+ | main = putStrLn (show (sort [3,1,2])) |
[[Category:Language extensions]] |
[[Category:Language extensions]] |
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Revision as of 03:25, 27 October 2016
The GHC Users Guide has Implicit Parameters section.html#{{{2}}} {{{3}}}.
Working example:
{-# LANGUAGE ImplicitParams #-}
import Data.List (sortBy)
sortBy' :: (?cmp :: a -> a -> Ordering) => [a] -> [a]
sortBy' = sortBy ?cmp
sort :: Ord a => [a] -> [a] sort = let ?cmp = compare in sortBy' main = putStrLn (show (sort [3,1,2]))