Changes between Version 4 and Version 5 of MultiParamTypeClassesDilemma


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Timestamp:
Feb 14, 2006 8:42:17 PM (8 years ago)
Author:
ravi@…
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  • MultiParamTypeClassesDilemma

    v4 v5  
    44 
    55== Options for solving the dilemma == 
    6  1. Examine a limited version of functional dependencies (are there any concrete proposals?) 
     6 1. Examine a limited version of functional dependencies (see below for one solution) 
    77 1. Put AssociatedTypes on the fast-track for sainthood 
    88 1. Punt: declare FunctionalDependencies as an extension and figure out a way to "bless" extensions 
     
    1515== Tickets == 
    1616 * [ticket:90 solve the MultiParamTypeClassDilemma] 
     17 
     18== Proposed Solutions == 
     191.  Adopt functional dependencies with the FD-conditions from the [http://research.microsoft.com/Users/simonpj/Papers/fd-chr/ CHR paper] together with the "complex relaxation rule" described at the bottom of the FunctionalDependencies page (also see the CHR paper, sect. 6). 
     20 
     21Pro:  
     22 * allows a safe version of FunctionalDependencies that can support the monad transformer library 
     23Con: 
     24 * complex specification for what is and is not allowed in classes and instance with functional dependencies 
     25 * not clear whether this could be forwards-compatible with associated types