[Haskell-cafe] Overload function application? (was: foldr (.) id)

[Greg Fitzgerald]

Should library functions target Control.Category?  We write for Num,
IsString, and ListLike.  Haskell overloads number literals and string
literals, and awkwardly not List literals.  Should Haskell overload
function application too?

How cool would it be to be able to leverage all of Haskell's libraries, and
effectively none of the runtime, by implementing instances for literals and
function application?  Say, for example, to generate a call graph, or make
the language strict, or target LLVM more directly.  Anyone tried this?

Thanks,
Greg


On Sat, Oct 27, 2012 at 11:39 AM, Greg Fitzgerald <garious at gmail.com> wrote:

> > Alternatively: flip (foldr id)
>
> Very cool, but...
>
> Prelude> import qualified Data.Foldable as F
> Prelude F> :t F.foldr id
> F.foldr id :: F.Foldable t => b -> t (b -> b) -> b
>
>
> {- Generalizing -}
>
> Prelude F> import qualified Control.Category as C
> Prelude F C> :t F.foldr (C..) C.id
> F.foldr (C..) C.id :: (F.Foldable t, C.Category cat) => t (cat b b) -> cat
> b b
>
>
> {- Sneaky type-specialization -}
>
> Prelude F C> :t F.foldr C.id
> F.foldr C.id :: F.Foldable t => b -> t (b -> b) -> b
>
>
> On Sat, Oct 27, 2012 at 3:09 AM, Ross Paterson <ross at soi.city.ac.uk>wrote:
>
>> On Fri, Oct 26, 2012 at 07:41:18PM +0100, Greg Fitzgerald wrote:
>> > I've recently found myself using the expression: "foldr (.) id" to
>> > compose a list (or Foldable) of functions.  It's especially useful
>> > when I need to map a function over the list before composing.  Does
>> > this function, or the more general "foldr fmap id", defined in a
>> > library anywhere?  I googled and hoogled, but no luck so far.
>>
>> Alternatively: flip (foldr id)
>>
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>
>
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