Changes between Version 31 and Version 32 of Status/May13


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Timestamp:
May 1, 2013 12:38:27 PM (12 months ago)
Author:
xnyhps
Comment:

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  • Status/May13

    v31 v32  
    3838  for all datatypes and classes defined in the module. 
    3939 
    40   * Type holes ['''Thijs Alkemade'''] 
     40  * '''Type holes.''' A GHC extension called [http://www.haskell.org/haskellwiki/GHC/TypeHoles Type Holes] was added by Thijs Alkemade, under supervision of Sean Leather and with help from Simon Peyton Jones. When GHC encounters a hole in an expression, written as "`_`", it will generate an error message describing the type that is needed in place of that hole. It gives some helpful additional information, such as the origins of the type variables in the hole's type and the local bindings that can be used. Together with {{{-fdefer-type-errors}}} this should make it easier to write code step-by-step, using hints from the compiler about the unfinished parts. 
    4141 
    4242  * '''Rebindable list syntax.''' A GHC extension called [wiki:OverloadedLists overloaded lists] was added by Achim Krause, George Giorgidze, and colleagues. When this is turned on, the way GHC desugars explicit lists and lists in arithmetic sequence notation is changed. Instead of directly desugaring to built-in lists, a polymorphic witness function is used, similar to the desugaring of numeric literals. This allows for a more flexible use of list notations, supporting many different list-like types. In addition, the functions used in this desugaring process are completely rebindable.