Changes between Version 33 and Version 34 of Status'


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Timestamp:
Sep 17, 2006 1:28:39 AM (8 years ago)
Author:
ravi@…
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  • Status'

    v33 v34  
    2020 
    2121The work on the class system has focused on resolving the MultiParamTypeClassesDilemma. The core of the dilemma is that multi-parameter typeclasses are a popular extension 
    22 that are strongly desired in Haskell'. However, many important uses of MPTCs (like the monad transformer library) require additional extensions to resolve ambiguities in their typechecking. Historically, FunctionalDependecies have been used for this purpose, but they are very tricky to implement and are also difficult to specify in a way that 
    23 guarantees the termination of typechecking. AssociatedTypes are a possible replacement, but they have not yet been completely implemented in any Haskell implementation. 
     22that is strongly desired for Haskell'. However, many important uses of MPTCs (like the monad transformer library) require additional extensions to resolve ambiguities in their typechecking. Historically, FunctionalDependencies have been used for this purpose, but they are very tricky to implement and are also difficult to specify in a way that 
     23guarantees the termination of typechecking. AssociatedTypes are a possible replacement, but our current implementation experience with them is very limited. The subcommittee has explored several ways to resolve this dilemma (including restricted FDs, fast-tracked ATs and FDs as a "blessed" extension), but, so far, no consensus has emerged. Our current plan is to focus on writing other parts of the Haskell' standard, in the hopes that additional implementation experience with ATs will clarify the situation. 
    2424 
    2525== Libraries ==