[Boost-bugs] [Boost C++ Libraries] #3114: Modified interface to allow even lazier return types for defaults

Subject: [Boost-bugs] [Boost C++ Libraries] #3114: Modified interface to allow even lazier return types for defaults
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-05-30 23:51:19

#3114: Modified interface to allow even lazier return types for defaults
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 Reporter:  jewillco      |       Owner:  danielw  
     Type:  Patches       |      Status:  new      
Milestone:  Boost 1.40.0  |   Component:  parameter
  Version:  Boost 1.38.0  |    Severity:  Problem  
 Keywords:                |  
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 There are some use cases where the return type of operator() in a default
 computation class is not valid in some cases when that default is not
 used.  The current interface to such classes does not allow that case; see
 the message at http://lists.boost.org/Archives/boost/2009/05/152009.php

 for more information.  The attached patch allows a special member type
 (that must be void) to be used to change the interface to pass a single
 int argument to operator(), while keeping the old no-parameter interface
 for function objects without the special tag.  The tag could also have
 been implemented as a traits class used with enable_if.  The patch passes
 all of the Boost.Parameter tests except two (which appear to freeze up).
 I only changed the normal path through the code, and not the compatibility
 code which I am unable to test.  A test for the new functionality added by
 the patch is also attached.

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Ticket URL: <https://svn.boost.org/trac/boost/ticket/3114>
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