Re: [Boost-bugs] [Boost C++ Libraries] #8564: Variable hiding errors within nested let blocks in Phoenix

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #8564: Variable hiding errors within nested let blocks in Phoenix
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-02-08 19:59:32

#8564: Variable hiding errors within nested let blocks in Phoenix
-------------------------------+---------------------
  Reporter:  miremare@…        |      Owner:  theller
      Type:  Bugs              |     Status:  new
 Milestone:  To Be Determined  |  Component:  phoenix
   Version:  Boost 1.53.0      |   Severity:  Problem
Resolution:                    |   Keywords:
-------------------------------+---------------------

Comment (by John Fletcher <J.P.Fletcher@…>):

 This is indeed a bug and the examples given do not work. The solution is
 to use either an argument e.g _1 or a local variable e.g.  _a to assign
 value to the local variable in the inner let.

 These examples both work with the definitions

 {{{
 namespace phoenix = boost::phoenix;
 using namespace phoenix::local_names;
 using boost::phoenix::arg_names::_1;
 using boost::phoenix::arg_names::_2;
 using boost::phoenix::arg_names::_3;
 using std::cout;
 }}}

 {{{
   phoenix::let(_x = _1, _y = _2)
   [
       let(_x = _3) // hides the outer _x
       [
        cout << _x << _y // prints "Hello, World"
       ]
   ](1," World","Hello,");
   cout << std::endl;
 }}}
 {{{
   phoenix::let(_x = _1, _y = _2, _z = _3)
   [
       let(_x = _z) // hides the outer _x
       [
        cout << _x << _y // prints "Hello, World"
       ]
   ](1," World","Hello,");
   cout << std::endl;
 }}}

 I will investigate further and also change the documentation.  John

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8564#comment:1>
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