Re: error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'std::string' (or there is no acceptable conversion)

From:
 James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Sun, 17 Jun 2007 14:07:13 -0000
Message-ID:
<1182089233.611931.224760@w5g2000hsg.googlegroups.com>
On Jun 17, 11:52 am, aarth...@gmail.com wrote:

I have written this code, and at the end, I am trying to write
a vector of strings into a text file. However, my program is
nor compiling, and it gives me the following error when I try
to write to the file:

error C2679: binary '<<' : no operator found which takes a right-hand
operand of type 'std::string' (or there is no acceptable conversion)

I don't know what I am doing wrong. I have posted my entire
program here.


It really would have been better if you'd have created a minimum
example.

#include <iostream>
#include <fstream>
#include <iterator>
#include <algorithm>
#include <vector>
#include <math.h>
#include "string.h"


As others have said, you haven't included <string>. So there's
no guarantee that you have all of the operations that are
normally provided for std::string.

using namespace std;

char n_str[2000];
char a_str[2000];

char n_char[2000];
char a_char[2000];
string achar, nchar;

int main(int argc, char* argv[])
{
        vector<string> n_word_list;
        vector<string> a_word_list;

        ifstream in_a("10_a.txt");
        if (!in_a)
        {
                cout << "Error opening abnormal file" << endl;
        }
        while (!in_a.eof())


This line is wrong. What you want is actually:

    std::string a_str ; // No point in reading into a C style
                          // array...
    while ( std::getline( in_a, a_str ) ) {
        a_word_list.push_back( a_str ) ;
    }

    [...]

        while (!in_n.eof())


Same comment as above.

        cout << n_word_list.size()<< endl;


And of course, this whole loop can be written as:

    std::copy( a_word_list.begin(), a_word_list.end(),
                std::ostream_iterator< std::string >( out_a,
"\n" ) ) ;
    out_a.close() ; // Since you're not using it any more...
    if ( ! out_a ) {
        std::cerr << "Write error in out_a" << std::endl ;
    }

As above.

        for (unsigned int i=0; i<n_word_list.size(); i++)
        {
                out_n << n_word_list.at(i) << endl; //ERROR
        }


Since (rather exceptionally for a beginner) you are doing
correct error checking, don't forget to check that your writes
actually worked.

--
James Kanze (Gabi Software) email: james.kanze@gmail.com
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