Thread: Creating Header Files

Hello everyone

I've been programming C++ casually for about half a year now, and my programs are starting to grow large. I've been monitoring these boards for some time now, and some times i see some of you gurus including and making your own header files for storing away classes and functions.

There's an entry in the FAQ about making headers, but i just can't get it to work properly, it's quite frustrating, here is my example application:

Code:

#include <iostream>
#include <windows.h>
#include <string.h>
#include "function.h"

using namespace std;

int main()
{
    char sentence1[] = "Why ain't this working!?";
    int length = strlen(sentence1);
    printout(sentence1, length, 100);
}

And the "function.h" header:

Code:

#ifndef _FUNCTION_H
#define _FUNCTION_H

inline void printout(char sentence[], int length, int interval)
{
     int x;
     for (x=0; x<length; x++)
     {
         cout<< sentence[x];
         Sleep(interval);
     }
}

#endif

All i get is a compiler error saying that printout is undeclared, i have tried everything, but to no prevail.

Thanks in advance

hmm... for one thing, you might need to #include <windows.h> in functions.h

Aside from that, have you tried testing with a simpler example?

Code:

#include "function.h"

int main()
{
    printHelloWorld();
}

then for function.h:

Code:

#ifndef FUNCTION_H
#define FUNCTION_H

#include <iostream>

void printHelloWorld()
{
    std::cout << "Hello world!" << std::endl;
}

#endif

I think Tropicalia means this:

Code:

#ifndef _FUNCTION_H
#define _FUNCTION_H

inline void printout(char sentence[], int length, int interval);

inline void printout(char sentence[], int length, int interval)
{
     int x;
     for (x=0; x<length; x++)
     {
         cout<< sentence[x];
         Sleep(interval);
     }
}

#endif

If you're using g++, then try something like
g++ -E prog.cpp > temp.txt

The temp.txt file will contain the result of all the #include and #if and #define statements. Look towards the end of the file to see if you're actually getting the file included.

Other compilers have similar flags for just running the pre-processor.

> #ifndef _FUNCTION_H
Pick another name. Everything which begins with _ is reserved, so you should avoid using it yourself.

Putting in prototypes like that and expecting it to work is plain silly. There is absolutely no point in having a prototype and immediately defining the function after that. Where prototypes come into play would be having the prototypes in the header file, and then having an implementation file to implement the functions.

I mean put the prototype before main, not in the header

That's not very useful either. The thing is, the OP's code should work, with a minor adjustment. Somehow, perhaps due to project settings, the header file is not getting included properly.

I've never implemented a function in a header file, so I don't know what's the problem in that code exactly. Just don't use header files for implementation, only declare them there. (As laserlight said)

Ah, a test compile of your original code reveals another error: you failed to fully qualify the names. Use std::cout instead of cout.