for_each, bind2nd and mem_fun_ref

[hk_mp5kpdw]

First off I am using either MSVC++ 6.0 or MS.NET on a C++ console application. I have some code that uses the for_each function to print out some data on a set of objects using the mem_fun_ref adapter to call the object's own print function. This all works fine if the object's print function doesn't have any parameters and can internally just use a specific output stream, cout for example:

#include <set>
#include <iostream>
#include <algorithm>
#include <functional>
using namespace std;

class tsv
{
public:
    // BTW... for .NET the function below works, but...
    // MSVC++ however insists on a non-const func returning a value in the for_each call below
    void print() const
    {
        // Output class data to cout for example
    }
};

int main()
{
    set<tsv> TsvSet;

    // Read in multiple tsv objects and insert them into the set

    // Now use for_each and tsv object's own print function for output to cout

    for_each( TsvSet.begin(), TsvSet.end(), mem_fun_ref(tsv::print) ); // Works just fine

    return 0;
}

What I want to have happen is to be able to have the object's print function accept a parameter to an ostream stream object so I could have my for_each function either output everything to cout for example at one point in the program or later output something to a file. I have been looking through Nicolai Josuttis' The C++ Standard Library: A Tutorial and Reference (8.2.2 Function Adapters for Member Functions) and he seems to say you can pass a single parameter to a function in this manner using bind2nd. For example:

#include <set>
#include <iostream>
#include <algorithm>
#include <functional>
#include <fstream>
using namespace std;

class tsv
{
public:
    void print(ostream& out) const
    {
        // Output class data to "out" ostream object
    }
};

int main()
{
    set<tsv> TsvSet;
    ofstream outfile("Output.Txt");

    // Read in multiple tsv objects and insert them into the set

    // Now use for_each and tsv object's own print function for output to outfile...
    // This does not work for me.

    for_each( TsvSet.begin(), TsvSet.end(), bind2nd(mem_fun_ref(tsv::print),outfile) );

    return 0;
}

In .NET I seem to get "reference-to-a-reference" errors using the bind2nd function, in MSVC++ I think I get "cannot deduce template argument" errors. Is there some trick I need to get this working? I have tried making the parameter const/non-const, reference/non-reference, this/that and it's starting to frustrate me. Either there is something simple I'm missing or I can't do this in this fashion. I can get around this by having my print function in a zero argument manner to print to a static ofstream member of my tsv class so that the for_each function can write all the objects to the same file but I would like to know if this at least possible.

[Prelude]

The only way I could get it to work after a few minutes was to have print take a pointer to an ostream instead of a reference. If you use a reference then bind2nd creates its own reference, resulting in a reference to a reference, which is illegal.

[hk_mp5kpdw]

Thanks, I will try messing around with that and see if I can get it to work.