On Mon, 9 Dec 2013, Simon Marlow wrote:
Is Haddock a part of GHC? I don't know. If it's not, then whatever
parser it's using will have to be extended to support pattern synonyms.
Haddock uses GHC's parser, but it will need to be taught about pattern
synonyms and how to render them in documentation.
OK, I'll add pattern synonym support for Haddock. We don't really have a
surface syntax for pattern types (yet?), so for now I'll just use this
format:
pattern P :: b -> a -> T a; requires (Num a); provides (Eq b)
Right, I'm not suggesting that we should break the abstraction, but I think
it would be really nice if there was a way to say "the following 3 patterns
are exhaustive", perhaps in a pragma.
One of the things that we ought to be able to do with this extension is to
provide abstract datatypes with pattern matching support. The only thing
missing is support for exhaustive pattern matches. F# active patterns has
it!
This should be something orthogonal to pattern synonyms that supports
regular view patterns as well.
If there's no separate Trac ticket for ViewPatternsAlternative yet, I'm
happy to open one.
That would be great!
I've added it as #8605.
Bye,
Gergo
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