[Boost-users] [bind] Surprising behavior

From: Christian Henning (chhenning_at_[hidden])
Date: 2007-04-16 15:58:14

Hi there, I'm sure it's not a bug in bind but I have found a
surprising behavior when using it. In my project I have to use some
old school c++ classes that use character arrays instead of
std::string. The following code displays a difference when using two
ways of printing those character arrays.

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>

#include <boost/bind.hpp>

using namespace std;
using namespace boost;

class A
{
public:
   A( string name )
   {
      strncpy( _name, name.c_str(), name.length() + 1 );
   }

   string name() const { return _name; }

private:
   char _name[80];
};

void print( const char* s )
{
   cout << s << endl;
}

int main(int argc, char* argv[])
{
   vector<A> as;
   as.push_back( A( "A" ));
   as.push_back( A( "B" ));

   for_each( as.begin()
           , as.end()
           , bind( &print
                 , bind( &std::string::c_str
                       , bind( &A::name, _1 ))));

   vector<A>::const_iterator it = as.begin();
   vector<A>::const_iterator end = as.end();

   for( ; it != end; ++it )
   {
      cout << it->name() << endl;
   }

         return 0;
}

The output should be

A
B
A
B

But instead it's

A
B

The foreach loop doesn't print anything. The problem is when calling
the print function the char* points to an empty string.  Can somebody
please enlightening, here.

Thanks,
Christian