Re: Lenses that work with Arrows
Tom Ellis <tom-lists-haskell-cafe-2013 <at> jaguarpaw.co.uk>
2013-10-07 18:57:37 GMT
On Mon, Oct 07, 2013 at 06:22:33PM +0100, Tom Ellis wrote:
> On Mon, Oct 07, 2013 at 07:14:44PM +0200, Niklas Haas wrote:
> > On Mon, 7 Oct 2013 10:40:13 +0100, Tom Ellis <tom-lists-haskell-cafe-2013 <at> jaguarpaw.co.uk> wrote:
> > > I introduce a very simple extension to the Lens datatype from Control.Lens
> > > that allows it to work with Arrows:
> > >
> > > https://gist.github.com/tomjaguarpaw/6865080
> > The reason we don't tend to have combinators like ‘view’ or ‘over’
> > generalized in their return profunctor like that is because you very
> > quickly run into type ambiguity issues.
> Perhaps I didn't explain clearly what I am asking for. The crux of the
> issue is whether it is possible *at all* to write the function
> overArr :: Arrow arr => Lens s t a b -> arr a b -> arr s t
> not whether it should be merged with over.
Edward Kmett has answered in the affirmative, which pleases me greatly!
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