#4894: Missing improvement for fun. deps.
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Reporter: diatchki | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler (Type checker) | Version: 7.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by simonpj):
Well, if you are going to propose some new form of evidence in FC, it'd be
good to be specific, and give the syntax, typing judgements, and
operational semantics. A good starting point is the appendix of
http://research.microsoft.com/en-us/um/people/simonpj/papers/ext-f/. I
don't yet understand the proposed extension.
Lacking such an extension, GHC's current position is to use fundeps for
improvement, for 'wanted' constraints but not for 'given' ones. If you
want to use the equalities for given ones, then use type functions.
I can believe that is sometimes infelicitous, but I didn't understand your
example. Can you give an example where the type-function version is
tiresome or annoying? Thanks.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4894#comment:5>
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