Compiling Helper file with functions

Question

I'm at a loss - i'm just getting into C++ and for some reason this is not working out for me. So i'm using Netbeans, and i've got the following main file:

#include <cstdlib>

#include "functions.h"

using namespace std;

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

    f("help");

    return 0;
}

Functions.h file:

#include <string>

#ifndef FUNCTIONS_H
#define FUNCTIONS_H

void f( string a );

#endif

and Functions.cpp file:

#include "functions.h"

void f( string a ) {
    return;
}

So, long story short, it doesn't compile. It says it can't understand the string variable? I don't get it, i tried moving the include for string all over the place but nowhere seems to help. What do i do?

You can think of the problem this way: it's real name isn't `string` -- it's `std::string`. Don't cheat by using `using namespace std;`. — John Dibling, Feb 05 '13 at 23:47
@user1288167: Yes, it's a bad practice. In short, it undos all the benefits of using namespaces in the first place. Learn to use namespaces, not work around them. — John Dibling, Feb 05 '13 at 23:50

score 2 · Answer 1 · edited May 23 '17 at 12:02

2

If you are attempting to use std::string, you have to #include <string> in your functions header, and call it std::string,since it is in the std namespace.

#ifndef FUNCTIONS_H
#define FUNCTIONS_H

#include <string>

void f( std::string a );

#endif

See this related post and also why is 'using namespace std' considered bad practice in C++?

edited May 23 '17 at 12:02

Community

1
1

answered Feb 05 '13 at 23:42

juanchopanza

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score 2 · Answer 2 · edited May 23 '17 at 10:24

2

You need to include string header file in Functions.h, also tell compiler that string is from std namespace.

#ifndef FUNCTIONS_H
#define FUNCTIONS_H

#include <string>
void f( std::string a );

#endif

Functions.cpp file:

#include "functions.h"

void f( std::string a ) {
    return;
}

Better practice is to pass string by const reference

void f(const std::string& a ) {
    return;
}

See Why is 'using namespace std;' considered a bad practice in C++?

edited May 23 '17 at 10:24

Community

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answered Feb 05 '13 at 23:42

billz

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Can I get around this by writing that "using namespace std;" line in my other files? Or is it good practice to write it in? – user1288167 Feb 05 '13 at 23:46
1

Yes you can but that's not good program practice. See my updated answer regarding `using namespace std;` – billz Feb 05 '13 at 23:46
2

@user1288167: Please don't get in to the bad habit of `using namespace std`. It will only cause you and your colleagues grief. – John Dibling Feb 05 '13 at 23:48
Ok, i'm not opposed to learning to not use it, but why does it cause grief? – user1288167 Feb 05 '13 at 23:49
1

@user1288167: Because of name ambiguity. See the link provided in bilz's answer for a pretty good explanation. – John Dibling Feb 05 '13 at 23:54

score 0 · Answer 3 · answered Feb 05 '13 at 23:42

0

Include the standard header: <string>

#include <string>

answered Feb 05 '13 at 23:42

Khaled Alshaya

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Compiling Helper file with functions

3 Answers3