i hate it when C++ fails to make any sense...

im trying to create a simple header file for a couple custom functions.

Code:

---

#include <iostream.h>
#include <conio.c>
#include <time.h>

void pause(int t);
int random(int u);


void pause(int t){
    int x;
    while ( x < 1000000000 ){
    x = x + t;
    }
}


int random(int u){
    int x;
    srand(time(NULL));
    x = ( rand() % u ) + 1;
    return x;
}

---

but when i go to compile the program, it gives me the errors:

redefinition of `void pause(int)'
`void pause(int)' previously defined here
redefinition of `int random(int)'
`int random(int)' previously defined here

and when i doubleclick the errors to see where they are, they both highlight the same line of code. basically, its telling me that those functions are previously defined by themselves! ive tried everything i can think of. whats the deal??

Code:

---

void pause(int t){
    int x;
    while ( x < 1000000000 ){
    x = x + t;
    }
}

---

x is undefined, therefore the behavior of this function is undefined.

Also, why do you need function prototypes if you flesh out the function directly underneath? It seems pointless to me.

Another thing, create an inclusion guard for your header...

#ifndef __RANDOM_PAUSE_H
#define __RANDOM_PAUSE_H

// .. code ..

#endif

edit: I think those names may already be taken... especially random(). Use a namespace or rename your functions.

Quote:

---

Originally posted by Eibro
why do you need function prototypes if you flesh out the function directly underneath? It seems pointless to me.

---

ive heard its good practice. and plus, when i expand the files more i like to see at a glance which functions ive included in which header/cpp files.

Quote:

---

Originally posted by Eibro
Another thing, create an inclusion guard for your header...

#ifndef __RANDOM_PAUSE_H
#define __RANDOM_PAUSE_H

// .. code ..

#endif

---

im not the most experienced programmer, and im not quite sure how to use inclusion guards or what the purpose of them is.

Quote:

---

Originally posted by Eibro
edit: I think those names may already be taken... especially random(). Use a namespace or rename your functions.

---

well, the pause() function worked when i had it in my main cpp file. as a matter of fact, it was even working at one point while it was in its current state. i just changed 'random()' to 'randomnumber()' and im still having the same problems.

Try this:

Code:

---

#include <iostream.h>
#include <conio.c>
#include <time.h>

#ifndef __RANDOM_PAUSE_H
#define __RANDOM_PAUSE_H

void pause(int t);
int random(int u);


void pause(int t){
    int x = 0; // Notice this
    while ( x < 1000000000 ){
    x = x + t;
    }
}


int random(int u){
    int x;
    srand(time(NULL));
    x = ( rand() % u ) + 1;
    return x;
}

#endif

---

that works... thanks. now can you explain to me what i just did?

(btw, when you create an int and dont assign it a number, it defaults to 0. the pause function works without setting x to 0)

Quote:

---

Originally posted by Eibro

Also, why do you need function prototypes if you flesh out the function directly underneath? It seems pointless to me.

---

It's quite useful, avoids problems if you misspell the function name. Bjarne Stroustrup explains this further in his book "The C++ Programming Language".

Actually CodeWarrior issues a warning if a function is defined without being declared.

Quote:

---

(btw, when you create an int and dont assign it a number, it defaults to 0. the pause function works without setting x to 0)

---

Don't rely on it.

Not on my compiler/system does an undefined value default to 0. Try:

Code:

---

int x;
cout << x;

---

What that inclusion guard does is defines the macro __RANDOM_PAUSE_H if it's not already defined, and includes the code in between the #if .. #endif macros at compile time. However, if the macro is defined... it your code is not included in the build. This results in a "guard" which prevents your header from being included twice, no matter how many times you actually include it.

Someone can probably explain it better than I.

Quote:

---

Originally posted by ...

(btw, when you create an int and dont assign it a number, it defaults to 0

---

only in static storage, not here

Quote:

---

Don't rely on it.

---

Quote:

---

Not on my compiler/system does an undefined value default to 0

---

Quote:

---

only in static storage, not here

---

ive been beaten into submission :)

and thanks, eibro. i learned something new today.