Re: [Boost-users] [Lambda] Help with if_then_else

From: Scott Meyers (usenet_at_[hidden])
Date: 2006-03-08 17:56:06

I tried both suggested solutions (applying var to cout, applying constant to the 
  output string -- see below), but neither works.  What follows is a complete 
compilation unit (not program -- there's no main) that fails with both VC7.1 and 
gcc 3.4.2 when I uncomment either of the two for_each loops.  The error messages 
are, um, not as enlightening as they might be.  Any suggestions how to get this 
to work?

Thanks,

Scott

#include <iostream>
#include <string>
#include "boost/filesystem/operations.hpp"
#include "boost/filesystem/path.hpp"
#include "boost/lambda/bind.hpp"
#include "boost/lambda/if.hpp"

void f(const std::string& dirName)
{
   using namespace std;

   namespace fs = boost::filesystem;
   fs::path dir(dirName, fs::native);

   using namespace boost::lambda;

//    for_each(fs::directory_iterator(dir), fs::directory_iterator(),
//             if_then_else(bind(&fs::is_directory, _1),
//                          cout << constant("D\n"),
//                          cout << constant("~D\n")));

//    for_each(fs::directory_iterator(dir), fs::directory_iterator(),
//             if_then_else(bind(&fs::is_directory, _1),
//                          var(cout) << "D\n",
//                          var(cout) << "~D\n"));

}