Proposal: Improving the IsString String instance
dag.odenhall at gmail.com
Mon Aug 26 22:34:52 CEST 2013
ExtendedDefaultRules already provides this to some extent, for example it
makes print "hello" work without type information.
On Mon, Aug 26, 2013 at 10:09 PM, Dan Burton <danburton.email at gmail.com>wrote:
> Just to throw another curveball at this conversation, what about a
> general, ad-hoc solution for 'typeclass defaults'? The logic goes like
> this: Is there an "ambiguous type variable" error due to the use of the
> IsString typeclass? Try defaulting to the String instance. If that doesn't
> work, try defaulting to Text. Repeat for a finite, explicit list of
> instances. If none of these defaults are successful, type error.
> We have hard-coded this sort of behavior into the Num class. Why not just
> provide this general capability for arbitrary classes? Or at least
> hard-code it into IsString as well.
> In the absence of this sort of solution, +1 to Edward's original proposal.
> The "o" proposal is not viable because the oft-needed parens make it
> confusing and irritating to the new Haskeller.
> -- Dan Burton
> On Mon, Aug 26, 2013 at 12:41 PM, Henning Thielemann <
> lemming at henning-thielemann.de> wrote:
>> On Mon, 26 Aug 2013, Gabriel Gonzalez wrote:
>> I'm guessing this is sarcastic, but I just want to clarify what I
>>> understood Henning's proposal to be. He's not saying we should provide an
>>> `o` function in the standard library, but rather encourage users to define
>>> their own.
>> Yes. I would be ok if packages provide this function, but I would urge
>> programmers to import that explicitly.
>> This one liner would take the place of the current line that they
>>> devote right now to `OverloadedStrings` .
>> However, the analogy is still apt since the exact same line of reasoning
>>> applies to overloaded numeric
>>> literals where we currently rely on defaulting to solve this problem.
>> I always use -Wall and thus I am warned about when defaulting takes
>> place. Thus I am confident that I do not rely on defaulting in my code.
>> Libraries mailing list
>> Libraries at haskell.org
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