[Boost-users] Implementing copy_if using boost::lambda

From: Minkoo Seo (minkoo.seo_at_[hidden])
Date: 2006-07-31 09:57:07

Hi list.

I'm trying to implment copy_if using boost::lambda:

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <iterator>
#include <map>

#include <boost/lambda/lambda.hpp>
#include <boost/lambda/if.hpp>
#include <boost/format.hpp>
#include <boost/lambda/bind.hpp>
#include <boost/lambda/algorithm.hpp>

using namespace std;
using namespace boost::lambda;

int main()
{
    vector<int> vi;
    vi.push_back(1);
    vi.push_back(2);
    vi.push_back(3);
    vi.push_back(4);
    vi.push_back(5);

    vector<int> vi2;

    for_each(vi.begin(), vi.end(),
             if_then(_1 == 1, vi2.push_back(_1)));

    return EXIT_SUCCESS;

}

This fails with the errors:

lambda_test.cpp: In function 'int main()':
lambda_test.cpp:30: error: no matching function for call to
'std::vector<int, std::allocator<int> >::push_back(const
boost::lambda::lambda_functor<boost::lambda::placeholder<1> >&)'
/usr/lib/gcc/x86_64-redhat-linux/4.0.2/../../../../include/c++
]/4.0.2/bits/stl_vector.h:602:
note: candidates are: void std::vector<_Tp, _Alloc>::push_back(const
_Tp&) [with _Tp = int, _Alloc = std::allocator<int>]

Does anybody know how to push _1 into vi2? I've tried bind( ), but no
luck.

Sincerely,
Minkoo Seo