Changes between Version 8 and Version 9 of Rank2Types


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Timestamp:
Feb 16, 2007 11:53:30 PM (7 years ago)
Author:
diatchki
Comment:

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  • Rank2Types

    v8 v9  
    2323The more general [wiki:RankNTypes] remove the last two restrictions. 
    2424 
     25'''Questions from Iavor:''' 
     26 * The restriction that polymorphic arguments have to be matched by variable or wildcard (`_`) patterns does not appear to be specific to rank-2 types---it seems like an orthogonal decision. 
     27 * While the rank-N proposal removes restriction (3), in many cases the results may be unexpected.  For example, consider the classic example of using {{{runST}}}: 
     28{{{ 
     29x = runST (return a)     -- OK 
     30y = runST $ return 'a'    
     31}}} 
     32 The rank-2 design rejects {{{y}}} because {{{runST}}} needs an extra argument.  The rank-N design accepts this use but later fails because the inferred type for '{{{runST}}}' is 'less polymorphic  than expected'. 
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    2540== References == 
    2641