Getline_input_to_int

[Neil.Dyke]

Hello,

Is it possible to convert the input you get from using the getline(inputfile, string) to an int?

Say i have a file "abcd.txt", with the following content:

6
3

How can i convert the 6 and 3, which are strings because of the getline() function, to an integer?

Thank you very much,

Neil.

[Lindley]

There are many ways to convert a string to an int. Some may be better than others for various situations:

sscanf()
istringstream
strtol()
atoi()
boost::lexical_cast

to name just a few.

[Neil.Dyke]

Thanks for your quick reply, i get an error whilst compiling though.

Heres my code:
<code>

#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
using namespace std;

int main()
{
ifstream diagram;
diagram.open("diagram.in");
string line;
int one;
int two;
getline(diagram, line);
one = atoi(line);
getline(diagram, line);
two = atoi(line);
system("PAUSE");
return 0;
}

</code>

The error i get is the following: error C2664: 'atoi' : cannot convert parameter 1 from 'std::string' to 'const char *'



- Neil.

[Lindley]

Yes, atoi() is a C function, so it doesn't know about std::string. The error is telling you exactly what's wrong. You'll need to use std::string's compatibility method, c_str().

[Philip Nicoletti]

Are there other chars on each line besides what you have shown ?
if not, whu not read directly into an int variable ?

[Neil.Dyke]

Thank you, Lindley. That helped!

@ Philip, is there a way i can read it directly into int?

- Neil.

[Philip Nicoletti]

int one , two;

diagram >> one >> two;