Re: Typing pattern synonyms

On 09/30/2015 08:10 PM, David Feuer wrote: > The Eq constraint is needed to support pattern matching, the raison d’être > of pattern synonyms. I'm pretty sure the reason you need > ScopedTypeVariables for your second example is that GHC only allows pattern > signatures with that extension enabled.

Typing pattern synonyms

The type of a pattern synonym like pattern FOO = 1234 seems to be '(Eq a, Num a) => a', which makes partially makes sense, although it's not immediately clear to me where the 'Eq a' part comes from. But probably that would be clear if I read the desugaring rules closely enough. ;-) My real

Re: Typing pattern synonyms

The Eq constraint is needed to support pattern matching, the raison d’être of pattern synonyms. I'm pretty sure the reason you need ScopedTypeVariables for your second example is that GHC only allows pattern signatures with that extension enabled. Once upon a time there was a separate

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Re: Typing pattern synonyms

2015-09-30 20:10 GMT+02:00 David Feuer : > The Eq constraint is needed to support pattern matching, the raison d’être > of pattern synonyms. > I was just a bit confused by the fact that normally you don't need an 'Eq a' constraint for pattern matching. But looking at the

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