[Haskell-cafe] Displaying specializations in :info or separately?

[Doug Burke]

Or

When t is []: find :: (a -> Bool) -> [a] -> Maybe a

if this really is for the newcomer!

Doug

On Mon, Oct 19, 2015 at 3:11 PM Richard Eisenberg <eir at cis.upenn.edu> wrote:

> I would avoid the `(t ~ []) =>` prefix -- it might be confusing to the
> newcomers this feature is meant to serve. How about
>
> With t := []: find :: (a -> Bool) -> [a] -> Maybe a
>
> ?
>
> Richard
>
> On Oct 19, 2015, at 12:47 PM, David Kraeutmann <kane at kane.cx> wrote:
>
> > Hi,
> >
> > I'm working on a GHC feature [1] that allows users to view
> > specializations of functions like in (name subject to change)
> >
> > ----
> >> :binfo find
> > find :: Foldable t => (a -> Bool) -> t a -> Maybe a
> > Specialisations:
> > t ~ [] => find :: (a -> Bool) -> [a] -> Maybe a
> >
> >> :binfo first
> > first :: Arrow a => a b c -> a (b, d) (c, d)
> > Specialisations:
> > a ~ (->) => first :: (b -> c) -> (b, d) -> (c, d)
> > ----
> >
> > Now there are two things left to decide on:
> > * What command should the specializations be visible under? We can
> > either put it under :info or make a special command :sinfo or :binfo
> > that displays only the expression's type and specialisations like in the
> > example above?
> >
> > * What specializations do we want to display? goldfire suggested using
> > the default list, which has the added benefit of being customizable by
> > e.g. instructors, so adding a default Maybe (in conjunction with [2])
> > gives the desired behavior and not too many specializations.
> >
> >
> > Thanks for your time!
> > David
> >
> >
> > ----
> > Links:
> > [1] : https://ghc.haskell.org/trac/ghc/ticket/10972
> > [2] : https://ghc.haskell.org/trac/ghc/ticket/10971
> >
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>
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