[sebwerner]

So im a newb at c++, been learning it for a month or so. Im trying to learn how to use header files and i've runned into this problem. I get errors saying that x,y,z isnt decleared, and i know why i get them, but I dont know why it dosent work. Why does it say that x,y,z isnt deceared when I decleared them in the header file? Im really stuck at this one...


main.cpp:

#include <iostream>
#include "header.h"

using namespace std;

int main(){
    
    while(1){
        cout<<"X: "<<x<<endl<<"Y: "<<y<<endl<<"Z: "<<z<<endl; //The x,y,z decleared in header.h
    }
    
}

header.h

#ifndef HEADER_H_INCLUDED
#define HEADER_H_INCLUDED
#include <windows.h>

int example(int x, int y, int z=0){

    if(GetAsyncKeyState(VK_UP)){y++;}
    if(GetAsyncKeyState(VK_DOWN)){y--;}
    if(GetAsyncKeyState(VK_RIGHT)){x++;}
    if(GetAsyncKeyState(VK_LEFT)){x++;}
    if(GetAsyncKeyState(VK_TAB)){z=1;}
    if(GetAsyncKeyState(VK_SPACE)){z=2;}
    if(GetAsyncKeyState(VK_SHIFT)){z=3;}

    return(0);
}

#endif // HEADER_H_INCLUDED

[Skydiver]

You declared x, y, and z as parameters to your example() function. You did not declare them as variables that main() can use.

[sebwerner]

Got it working by making the x,y,z variables global scope,
and put the "example();" in the main loop like this, Thank You Skydiver!

#include <iostream>
#include "header.h"

using namespace std;

int main(){
    
    while(1){
        example();
        cout<<"X: "<<x<<endl<<"Y: "<<y<<endl<<"Z: "<<z<<endl; //The x,y,z decleared in header.h
    }
    
}

[prabh]

Look for comments i put.
Your main.cpp should look something like this

#include <iostream>
#include "header.h"
using namespace std;

int main()
{
// the correct way
    int x= 0;
    int y= 0;
    int z = 0;
    cout << "Hello world!" << endl;
    while(1){
// to update your x,y and z you should call your function
        example(x,x,z);
	        cout<<"X: "<<x<<endl<<"Y: "<<y<<endl<<"Z: "<<z<<endl; //The x,y,z decleared in header.h
	    }
    return 0;
}

header.h

#ifndef HEADER_H_INCLUDED
#define HEADER_H_INCLUDED
#include <windows.h>

int example( int x,int y,int z){

    if(GetAsyncKeyState(VK_UP)){y++;}
    if(GetAsyncKeyState(VK_DOWN)){y--;}
    if(GetAsyncKeyState(VK_RIGHT)){x++;}
    if(GetAsyncKeyState(VK_LEFT)){x++;}
    if(GetAsyncKeyState(VK_TAB)){z=1;}
    if(GetAsyncKeyState(VK_SPACE)){z=2;}
    if(GetAsyncKeyState(VK_SHIFT)){z=3;}

    return(0);
}

#endif // HEADER_H_INCLUDED

This code compiled, but thats a horrible way to use while loop.
You need to learn a lot buddy.

[sebwerner]

I tried to do it the way you showed me here, but now the values wont in/de-crement when i press the arrowkeys:

[aresh]

prabh, you are passing arguments by value, so the changed value won't be reflected back in main.

[sebwerner]

I got it working, by doing what Skydiver siad

[yothsoggoth]

prabh's example should work pretty well, if you simply change line 5 as follows:

int example( int &x,int &y,int &z)

(Edit) Fixed tags

This post has been edited by yothsoggoth: 02 October 2012 - 02:51 AM

[aresh]

Well, I know that. But, I just pointed out his mistake

[joshua201]

Skydiver fixed it already

[aresh]

What the hell are you talking about? I am talking about correcting prabh's mistake!

[sebwerner]

yothsoggoth, on 02 October 2012 - 02:51 AM, said:

prabh's example should work pretty well, if you simply change line 5 as follows:

int example( int &x,int &y,int &z)

(Edit) Fixed tags

Why does it work if i put the "&" iin front of the variables? Im just wondering, after all im here to learn

[aresh]

Well, the & means that you are passing the variables by reference.

[jimblumberg]

Also note that you should not have function implementations inside header files, except when dealing with templates. C++ source should be placed in source files (.c, .cpp, etc) then added to your project not included using the #include statement.

Jim

[sebwerner]

aresh, on 02 October 2012 - 06:17 AM, said:

Well, the & means that you are passing the variables by reference.

Thank you!