Re: [Boost-bugs] [Boost C++ Libraries] #8749: Accessing type of insert<map<>, pair<A, B> >::type discards inserted elements

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #8749: Accessing type of insert<map<>, pair<A, B> >::type discards inserted elements
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-10-14 15:51:57

#8749: Accessing type of insert<map<>, pair<A,B> >::type discards inserted
elements
-------------------------------+-----------------------
  Reporter:  guylaingreer@…    |      Owner:  agurtovoy
      Type:  Bugs              |     Status:  new
 Milestone:  To Be Determined  |  Component:  mpl
   Version:  Boost 1.52.0      |   Severity:  Problem
Resolution:                    |   Keywords:
-------------------------------+-----------------------

Comment (by anonymous):

 This bug just bit me as well.  I'm just learning MPL, so maybe this isn't
 the best way, but I was writing a little map insertion lambda..


 {{{
 typedef lambda<
     eval_if<
         has_key<_1, key_type<_1, _2>>,
         identity<_1>,
         insert<_1, _2>
     >
 >::type insert_if_new;
 }}}

 Which, based on the docs I have read, should clearly work, but it fails
 without the typedef above.  This is on 1.56

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8749#comment:1>
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