[Boost-users] FOREACH with maps

From: Dave Steffen (dgsteffen_at_[hidden])
Date: 2005-05-10 16:39:15

Another question about the to-be-released FOREACH macro, which I find
I am using heavily... (BTW - Thanks Eric for your quick responses, and
for the cool macro!)

The issue is declaring the 'loop variable' for maps.  For example,

 vector<int> v;
 ...
 FOREACH (int a, v) { ... }   // this compiles
 int b;
 FOREACH (b, v) {...}  // this also compiles

However, for maps, the second variation (declaring outside the macro)
doesn't work:

 map<int,int> m;
 ...
 FOREACH (map<int,int>::value_type i, m) {...}  // compiles
 map<int,int>::value_type i;
 FOREACH (i, m) {...}                     // COMPILE ERROR

Specifically, the compiler says 

error: non-static const member 
` const int std::pair<const int,int>::first', 
can't use default assignment operator

(from GCC 3.3.1).  Despite my best efforts, I can't figure out what
this error means, or what it's talking about.  Anybody else run into
this?  Any thoughts?

----------------------------------------------------------------------
Dave Steffen, Ph.D.       "The only justification for our concepts and 
Software Engineer IV       systems of concepts is that they serve to 
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dgsteffen_at_[hidden]