Changes between Version 3 and Version 4 of NewAxioms/CoincidentOverlap


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Timestamp:
May 29, 2013 2:31:21 PM (11 months ago)
Author:
goldfire
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  • NewAxioms/CoincidentOverlap

    v3 v4  
    2828== Coincident overlap within a branched instance == 
    2929 
     30This section discusses a part of the "Concrete Proposal" on [wiki:NewAxioms/Nonlinearity this page] to patch a potential hole in Haskell's type system. 
     31 
    3032I (Richard) would like to be able to say this: 
    3133 
     
    5658 
    5759The ideas discussed here stem from posts by AntC, Andy Adams-Moran, and Richard on Richard's [http://typesandkinds.wordpress.com/2013/04/29/coincident-overlap-in-type-families/ blog post] on the subject. 
     60 
     61== Cross-module coincident overlap (or lack thereof) == 
     62 
     63[wiki:NewAxioms/Nonlinearity This proposal] has the net effect of forcing all uses of coincident overlap to appear in one module, instead of spread across modules. That's admittedly not great, but it's possible that no one will be negatively affected. The only alternative we've (Simon, Dimitrios, Richard) thought of is to disallow coincident overlap when the left-hand sides are non-linear, but that seems very ugly and ad-hoc.