#13572: Add ArgMin / ArgMax pattern synonyms -------------------------------------+------------------------------------- Reporter: Iceland_jack | Owner: (none) Type: feature request | Status: new Priority: normal | Milestone: Component: libraries/base | Version: 8.0.1 Resolution: | Keywords: | PatternSynonyms Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: None/Unknown | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Description changed by Iceland_jack: @@ -20,1 +20,1 @@ - pattern ArgMax [maxArg, maxValue} = Max (Arg maxArg maxValue) + pattern ArgMax {maxArg, maxValue} = Max (Arg maxArg maxValue) New description: {{{#!hs import Data.Semigroup pattern ArgMin :: a -> b -> ArgMin a b pattern ArgMin a b = Min (Arg a b) pattern ArgMax :: a -> b -> ArgMax a b pattern ArgMax a b = Max (Arg a b) }}} Or even record pattern synonyms, à la [https://github.com/energyflowanalysis/efa-2.1/blob/3eb86c0b6b2d2fb66cd5b76ce... this] {{{#!hs pattern ArgMin :: a -> b -> ArgMin a b pattern ArgMin {minArg, minValue} = Min (Arg minArg minValue) pattern ArgMax :: a -> b -> ArgMax a b pattern ArgMax {maxArg, maxValue} = Max (Arg maxArg maxValue) }}} and we can define {{{#!hs import Data.Semigroup.Foldable argmin :: Ord k => Foldable1 f => (a -> k) -> (f a -> a) argmin f = minValue . foldMap1 (\a -> ArgMin (f a) a) argmax :: Ord k => Foldable1 f => (a -> k) -> (f a -> a) argmax f = maxValue . foldMap1 (\a -> ArgMax (f a) a) }}} -- -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/13572#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler