CODEWITHSUNDEEP
c
minenerd
minenerd

Reputation: 3

Calculator and a floating point modulus function in C

I have to write a case for a '%' (modulus) function for a calculator. When I compile, it tells me I have used the fmod function incorrectly. Without the case '%', the rest of the code works as it should.

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>    // Originally missing

#define MAXOP 100
#define NUMBER '0'

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

main()
{
    int type;
    double op2;
    char s[MAXOP];

    printf("\nEnter numbers below in the following format\nwith a space between each:\n");
    printf("\tnum1 num2 operator\n");
    printf("\tyou may use (+, -, /, *) for the operators\n");

    while((type = getop(s)) != EOF)
    {
        switch(type)
        {
            case NUMBER:
                push(atof(s));
                break;

            case '+':
                push(pop() + pop());
                break;

            case '*':
                push(pop() * pop());
                break;

            case '-':
                op2 = pop();
                push(pop() - op2);
                break;

            case '/':
                op2 = pop();
                if(op2 != 0.0)
                    push(pop() / op2);
                else
                    printf("error: zero divisor\n");
                break;

              case '%':
                op2=pop();
                if(op2 != 0.0)
                    push(fmod(pop(),op2));
                else
                    printf("error: zero divisor");
                break;

            case '\n':
                printf("\t%.8g\n", pop());
                break;
            default:
                printf("error: unknown command %s\n", s);
                break;
        }
    }
    return 0;
}

I looked up the fmod function, and I still can not figure out why it will not work. Any thoughts?

I added the math.h header, and the error message I am getting now is:

/tmp/ccgiVhWI.o: In function `main':
calc.c:(.text+0x14f): undefined reference to `fmod'
collect2: ld returned 1 exit status

Upvotes: 0

Views: 131

Answers (2)

ooga
ooga

Reputation: 15511

You're missing the math.h header to provide the prototype for fmod.

Upvotes: 2

Jonathan Leffler
Jonathan Leffler

Reputation: 755016

You are missing #include <math.h> so the compiler thinks fmod() is a function returning int, or it is complaining that it knows about fmod() but you've not declared it properly, or thereabouts.

You would do better to include the exact compiler error message (unless there's a very long path for the file name, in which case truncating the file name would be a courtesy).

Upvotes: 2

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