Help using Header Files

This is a discussion on Help using Header Files within the C Programming forums, part of the General Programming Boards category; As my first post in the CProgramming forum i wanted to start off by saying hello and thanks in advance ...

  1. #1
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    Help using Header Files

    As my first post in the CProgramming forum i wanted to start off by saying hello and thanks in advance for any help I will receive.

    I am having trouble using header files. I am making a game, sort of like pac man, and I wanted to know how to make and use header files better. I have looked at several tutorials online but I cant seem to find anything that helps enough!!

    I basically wanted a little guideline on how to make header files so that I can have most of my algorithms for the game in there. Basically so I can keep my OpenGL code different to my code for controlling the game, e.g. functions I have for AI. I can post my code if it would help and any other advice is welcome.

    Thanks again!!

  2. #2
    and the Hat of Guessing tabstop's Avatar
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    You wouldn't put any of that into header files. Header files, in C, would (should, anyway) only contain function declarations, typedefs and struct definitions, and #defines. Look at say math.h in your standard library for an example.

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    Header files don't contain any algorithms themselves, they would only contain declarations, typedefs, global variables, etc.

    So where do you put the algorithms themselves? you keep them in another .c file, which must be compiled and linked to your main file.

    e.g. Lets say we have a function WriteUsage() that we want to place in a separate file and add it using a header file. We'll have 2 extra files (of course the file names are just examples):
    1. writeusage.c
    2. writeusage.h
    Now, writeusage.c will contain the function body, and will look something like this:
    Code:
    #include "writeusage.h"    //You don't need to include this header, however it is preferable since you can keep all the standard headers you need inside it
    void WriteUsage(void)
    {
        printf("usage: program filename options\n");
    }
    writeuser.h will look like this:
    Code:
    #include <stdio.h>
    
    void WriteUsage(void)
    Your main file will look like something like this:
    Code:
    #include "writeusage.h"
    int main(int argc, char *argv[])
    {
        ...
        if (something's wrong with the arguments)
        {
            WriteUsage();
            do whatever you want
        }
        ...
        return 0;
    }
    Now when you want to compile it, you'll need to inform the compiler to compile wrtieusage.c, and the linker to link its object file to your program like this:
    Code:
    gcc main.c writeusage.c
    I might not be a pro, but I'm usually right

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    Thnx alot Abda92! Should be able to use that to make my program a bit more manageable. Will give it a go and get back to you.

    As a note, im working on a mac using XCode. Would you know how I link through XCode! I'll have a go with it anyway and get back to you!

    Thnx alot again!

  5. #5
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    Ok I have tried doing as you said, and I'm sorry if this is something really small that I'm doing wrong but I just cant see the problem so hopefully you can help me with this. Thnx in advance!

    My "robotusage.c" looks like this:
    Code:
    #include "robotusage.h"
    
    int incrementI(int num, int dir)
    {
     if (dir == 1)
      return num += 4;
     else return num -= 4;
    }
    My robotusage.h looks like this:
    Code:
    #include <stdlib.h>
    #include <stdio.h>
    #include <GLUT/glut.h>
    
    int incrementI(int num, int dir)
    The part of the main.c that is using this code is:
    Code:
    player.pointX = incrementI(player.pointX, 1);
    And it gives me an "error:syntax error before "{" token" in the robotusage.c file. I cant seem to find what I've done wrong.

    I would post all of the main.c as well but its quite big until I can sort this stuff out. Thnx again!

  6. #6
    Nub SWE
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    You need a semicolon in your .h file after your function prototype.
    Code:
    #include <stdlib.h>
    #include <stdio.h>
    #include <GLUT/glut.h>
    
    int incrementI(int num, int dir);
    Last edited by JDGATX; 04-21-2008 at 01:59 PM. Reason: Because I am an idiot.

  7. #7
    Registered User Codeplug's Avatar
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    Quote Originally Posted by d34n View Post
    My robotusage.h looks like this:
    Code:
    #include <stdlib.h>
    #include <stdio.h>
    #include <GLUT/glut.h>
    
    int incrementI(int num, int dir)
    Put a semicolon at the end of that last line.

    gg

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    Thnx alot guys! I hate those little things. Thnx again!

  9. #9
    CSharpener vart's Avatar
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    Code:
    int incrementI(int num, int dir)
    {
     if (dir == 1)
      return num += 4;
     else return num -= 4;
    }
    No sence to use += and -= here

    Code:
    int incrementI(int num, int dir)
    {
     if (dir == 1)
      return num + 4;
     
     return num - 4;
    }
    The first 90% of a project takes 90% of the time,
    the last 10% takes the other 90% of the time.

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