undefined symbols

Working on a mac and getting an 'undefined symbols' error when I try to compile this push pop program. I don't see a problem in my code; I'm wondering if it could be a problem with the gcc version I have? If anyone can help it would be most appreciated :)

Here's my code:

Code:

---

#include <stdio.h>
#include <stdlib.h>                /* for atof() */

#define MAXOP        100                /* max size of operand or operator */
#define NUMBER        '0'                /* signal that a number was found */

int getop (char []);
void push (double);
double pop (void);

/* reverse Polish calculator */
main()
{
        int type;
        double op2;
        char s[MAXOP];
       
        while ((type = getop(s)) != EOF)
        {
                switch (type)
                {
                case NUMBER:
                        push (atof(s));
                        break;
                case '+':
                        push(pop() + pop());
                        break;
                case '*':
                        push(pop() * pop());
                        break;
                case '-':
                        push(pop() - op2);
                        break;
                case '/':
                        op2 = pop();
                        if (op2 != 0.0)
                                push(pop() / op2);
                        else
                                printf("error: zero divisor\n");
                        break;
                case '\n':
                        printf("\t%.8g\n", pop());
                        break;
                default:
                        printf("error: unknown command %s\n", s);
                        break;
                }
        }
        return 0;
}

---

Here's my error:

Code:

---

/usr/bin/ld: Undefined symbols:
_getop
_pop
_push
collect2: ld returned 1 exit status

---

> void push (double);
This is a prototype, it only tells the compiler that the function exists somewhere.

You need to actually implement it as well

Code:

---

void push (double) {
  // your code here
}

---

Thanks, I had a feeling that might have been the case...I added in the missing functions and it works now :)

There seems to be a flurry of these RPN calculators lately. The funny thing (for me) is I've just written one too, after a fashion - a very very poor Forth implementation that, at this very moment, is half crippled.

Just an aside.

>a very very poor Forth implementation that, at this very moment, is half crippled.
How does one write a "very poor" Forth implementation?

I think that's his attempt at being modest by doubting his own ability.

It hasn't got a dictionary. Actually I don't think it qualifies as a Forth. The most it can do is something like:

Code:

---

120 23 + .s drop

---

It started life as one of my many fiddles with writing a tokeniser.
EDIT:
>> Actually I don't think it qualifies as a Forth

By that I mean I don't think it complies with the standard. I'll go have a look-see now.