[Haskell-cafe] conflicting variable definitions in pattern

Sittampalam, Ganesh ganesh.sittampalam at credit-suisse.com
Fri May 15 06:30:38 EDT 2009


Conor McBride wrote:
> On 15 May 2009, at 09:11, Sittampalam, Ganesh wrote:
>>
>> but then pattern matching can introduce Eq constraints which some
>> might see as a bit odd.
> 
> Doesn't seem that odd to me. Plenty of other language features come
> with constraints attached. 

It's the introduction of a constraint from tweaking a pattern that is
odd, I think. By way of precedent H98 rejected this kind of idea in
favour of putting 'fail' into Monad.

Ganesh

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