Machine epsilon estimation in C

Question

I'm new to C and I'm trying to find machine epsilon (1.0 + macheps > 1.0), eta (eta > 0.0) and MAX (MAX < infinity), but my code doesn't work as intended. First of all, macheps is calculated using 80-bit precision. How do I force it to single, double and long double? Secondly, the code doesn't finish calculating the results for double precision at all.

EDIT: Fixed the format error.

/* macheps eta max */

#include <stdio.h>
#include <math.h>
#include <float.h>
#define TYPE long double

int main(void)
{
    TYPE macheps = (TYPE) 1.0;
    TYPE eta = (TYPE) 1.0;
    TYPE maksymilian = (TYPE) 2.0;
    TYPE real_macheps;
    TYPE real_eta;
    TYPE real_maksymilian;

    TYPE something = (TYPE) 1.0 + (TYPE) macheps;

    while ((TYPE) something > (TYPE) 1.0)
    {
        real_macheps = (TYPE) macheps;
        printf("%e ", (TYPE) real_macheps);
        macheps = (TYPE) macheps/(TYPE) 2.0;
        something = (TYPE) 1.0 + (TYPE) macheps;
    }
    printf("%e\n", (TYPE) real_macheps);

    while ((TYPE) eta > (TYPE) 0.0)
    {
        real_eta = (TYPE) eta;
        eta = (TYPE) eta/(TYPE) 2.0;
    }
    printf("%e\n", (TYPE) real_eta);

    while ((TYPE) maksymilian != INFINITY)
    {
        (real_maksymilian) = (TYPE) maksymilian;
        maksymilian = (TYPE) maksymilian*(TYPE) 2.0;
    }
    real_maksymilian = (TYPE) real_maksymilian * (TYPE) (2.0-(TYPE) real_macheps);
    printf("%e\n", (TYPE) real_maksymilian);
}

EDIT2: Shouldn't the above code force precision? What am I missing?

EDIT3: Still doesn't give correct macheps for long double.

Answer 1

You program will invoke undefined behavior. In C, long means long int and not long double.