New subject: boost::lambda library, error with << operator (on g++ with SGI STL)

9 Jul 2007

      Hi,
I've tried to compile the following code on linux/g++ (version 3.3.4
and 4.1.2), boost version 1.34:

-- CODE BEGINS --

#include <iostream>
using namespace std;

#include "boost/function.hpp"
#include "boost/ref.hpp"
using namespace boost;

#include "boost/lambda/lambda.hpp"
#include "boost/lambda/bind.hpp"
#include "boost/lambda/if.hpp"
using namespace boost::lambda;

int main(int argc, char *argv[]) {

  function f =
    if_(_1 == _2) [
            cout << cref("arguments are equal\n")
    ].else_[
            cout << cref("arguments differ\n")
    ];

  f(1, 1);
  f(1, 2);
}

-- CODE ENDS --

On g++ 3.3.4 I got a (scarcely readable) error that std::ios_base copy
constructor is private (the more recent compiler gave much more trashy
output, but I've infered that the reason is probably the same).

The error wouldn't appear if I had supplied at least one placeholder
to the operator<< in both if's cases in the lambda expression above.

Is there any way to overcome this limitation?

boost::lambda library, error with << operator (on g++ with SGI STL)

Maciek Godek

Kirit Sælensminde

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