Re: [Boost-bugs] [Boost C++ Libraries] #3225: boost::fusion sequence throws compiler error when used with boost::mpl::is_sequence

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #3225: boost::fusion sequence throws compiler error when used with boost::mpl::is_sequence
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-06-27 03:40:34

#3225: boost::fusion sequence throws compiler error when used with
boost::mpl::is_sequence
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 Reporter:  Jeffrey Hellrung <jhellrung@…>         |       Owner:  djowel 
     Type:  Bugs                                   |      Status:  new    
Milestone:  Boost 1.40.0                           |   Component:  fusion 
  Version:  Boost 1.39.0                           |    Severity:  Problem
 Keywords:  fusion mpl is_sequence                 |  
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Comment(by Jeffrey Hellrung <jhellrung@…>):

 Thanks for the quick reply!

 My intent was to provide a compile-time check that the types within the
 boost::fusion sequence satisfied certain properties.  Any boost::mpl-
 compatible code could thus be used for such checks, but some of the code
 I've written using boost::mpl has asserts that the sequences satisfy
 boost::mpl::is_sequence.  Otherwise, I would indeed construct the type
 sequence through boost::mpl and at the end convert it to a boost::fusion
 sequence, as suggested in the documentation.

 It's not just that a boost::fusion sequence fails to satisfy
 boost::mpl::is_sequence, but that attempting to apply a boost::fusion
 sequence to boost::mpl::is_sequence results in a compiler error, which is
 not the case for other non-boost::mpl-sequence types (I think).  The
 compiler error looks somewhat similar to what happens when trying to apply
 boost::mpl::fold to a fusion sequence, so I'll post a trac ticket for that
 code example and see what you think before forwarding these problems onto
 boost::mpl.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/3225#comment:3>
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