[Haskell-cafe] New type of ($) operator in GHC 8.0 is problematic

Tristan Seligmann mithrandi at mithrandi.net
Sun Feb 7 15:24:10 UTC 2016


On Sun, 7 Feb 2016 at 17:16 Richard Eisenberg <eir at cis.upenn.edu> wrote:

>
> I would agree with this... except that the version of ($) in base in 7.8
> and 7.10 already *was* generalized in this way. But no one got as itchy
> about the OpenKind that appears in 7.10's `:i $` as they are about the guck
> that appears in 8.0's `:t ($)`. So moving it out now would break code in
> the wild like https://ghc.haskell.org/trac/ghc/ticket/8739


My GHC 7.10 doesn't seem to have any OpenKind stuff:

GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help
Prelude> :i $
($) :: (a -> b) -> a -> b        -- Defined in ‘GHC.Base’
infixr 0 $
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