[Boost-bugs] [Boost C++ Libraries] #8187: Bug in phoenix docs and example code

Subject: [Boost-bugs] [Boost C++ Libraries] #8187: Bug in phoenix docs and example code
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-02-26 23:41:07

#8187: Bug in phoenix docs and example code
------------------------------+---------------------------------------------
 Reporter:  eric_niebler      |       Owner:  theller 
     Type:  Bugs              |      Status:  new     
Milestone:  To Be Determined  |   Component:  phoenix 
  Version:  Boost 1.52.0      |    Severity:  Cosmetic
 Keywords:                    |  
------------------------------+---------------------------------------------
 The example
 [http://www.boost.org/libs/phoenix/doc/html/phoenix/examples/transforming_the_expression_tree.html

 here] is leading people astray. It is not recursively applying the
 transformation for node types other than plus, minus, multiplies and
 divides. If the top-most node is not one of those, no transformation
 happens.

 The default case shown is:

 {{{
 struct invert_actions
 {
     template <typename Rule>
     struct when
         : proto::_ // the default is proto::_
     {};
 };
 }}}

 I think it should be:

 {{{
 struct invert_actions
 {
     template <typename Rule>
     struct when
       : proto::nary_expr<
             proto::_,
             proto::vararg<
                 proto::when<proto::_, evaluator(proto::_, _context)>
             >
         >
     {};
 };
 }}}

 I'm actually not quite sure how this works, but it seems to. Note that the
 problem would also need to be fixed
 [http://www.boost.org/libs/phoenix/example/invert.cpp here].

 See [http://stackoverflow.com/questions/15077637/transforming-a-boost-c

 -phoenix-expression-tree] for a discussion.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8187>
Boost C++ Libraries <http://www.boost.org/>
Boost provides free peer-reviewed portable C++ source libraries.