error: invalid initialization of reference of type 'std::istream&'

[adny]

Here we go again... I wrote a short program that tries to identify how many words are in a input stream. These are the source files and the header file:

4_exercise_5_read_function.h

#ifndef GUARD_4_exercise_5_read_function_h
#define GUARD_4_exercise_5_read_function_h
#include <iostream>
#include <string>
#include <vector>
std::istream& read(std::istream&, std::vector<std::string>&);
#endif 

4_exercise_5_read_function.cpp (the function that tries to create a vector from a input line)

#include "4_exercise_5_read_function.h"
using std::istream; using std::vector;
using std::string;
istream& read(istream& is, vector<string>& v)
     {
     if (is)
        {
         v.clear();
         string x;
         while (is >> x)
         v.push_back(x);
         // clear the error state of the stream so that input will work next time
         is.clear();
        }
     return is;
     }

4_exercise_5.cpp (main file)

#include <algorithm>
#include <iomanip>
#include <ios>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include "4_exercise_5_read_function.h"
using std::cin; using std::sort;
using std::cout; using std::streamsize;
using std::endl; using std::string;
using std::vector; using std::istream;
int main()
{
    string cis;
    vector <string> vec;
    typedef vector <string>::size_type vec_sz;
    read(cis, vec);
    vec_sz size = vec.size();
    cout << "The number of words of the given line is: " <<size<<endl;
    return 0;
}

And the errors are:

4_exercise_5.cpp In function 'int main()':|
4_exercise_5.cpp on line 18: error: invalid initialization of reference of type 'std::istream&' from expression of type 'std::string'|
4_exercise_5_read_function.h on line  6: error: in passing argument 1 of 'std::istream& read(std::istream&, std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > >&)'|

I don't know what could cause those error. And I really searched a solution. The parameters of read function are lvalues, they have the same types. Maybe I can't read a vector of strings like that? Can you give me a soulution?

[firedraco]

On line 18 you are passing a string as your first element, but your function expects an istream.

[adny]

yes. I understand. But how can I repair that? Can you be more specific?

[Galik]

What are you hoping to achieve by passing variable cis to function read()?

[adny]

cis (=console input stream) represents the place where I want to store the line that i want to read from the console. After that (using cis as an argument for the read function) I want to store the words from cis into a vector (v). That's the purpose of read function: introduces each word from the input stream (example):

Not only the universe is infinite

into a vector:

v[0]=not
v[1]=only
v[2]=the 
etc.

but it's not working...

[Galik]

If you have your input in string cis, then you need to turn that into an input stream. The std::istringstream is designed for exactly that purpose:

std::string cis;
std::istringstream iss(cis); // make an input stream from your string

// ...

read(iss, vec); // now call read with the input stream containing your string 

[adny]

thanks. but I just found another solution... :) it sound just like yours but a little shorter:

I deleted:

string cis;

and i changed:

read(cis, vec); to read(cin, vec);

and it works perfect.