Proposal: Improving the IsString String instance

Edward Kmett ekmett at
Mon Aug 26 23:30:26 CEST 2013

What i mean is that, there are a few users like Oren who have written
instances like

instance IsString [String] for parsing dotted quads or what have you.

those would be the kinds of thing that would become o :: String ->
[String], the stuff that couldn't be implemented without overlapping the a
~ Char => IsString [a] instance.

That said, I think Ganesh's proposal should work, so its moot.


On Mon, Aug 26, 2013 at 5:18 PM, Ian Lynagh <igloo at> wrote:

> On Mon, Aug 26, 2013 at 04:41:43PM -0400, Edward Kmett wrote:
> > The argument in favor of using some 'o' combinator works even better on
> my
> > side of the debate. ;)
> >
> > I can coopt the suggestion of 'o' to say that you can use it for the few
> > instances of IsString [Foo] that you want
> But under your proposal (assuming you mean the original proposal), there
> wouldn't be an IsString [Foo] instance, would there? So o = fromString
> wouldn't work for [Foo]?
> Thanks
> Ian
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