gistfile1.txt

# Infinity arithmetic in C

  -50.0	+   -50.0	=  -100.0
  -50.0	*   -50.0	=  2500.0
  -50.0	+     0.0	=   -50.0
  -50.0	*     0.0	=    -0.0
  -50.0	+    50.0	=     0.0
  -50.0	*    50.0	= -2500.0
  -50.0	+     inf	=     inf
  -50.0	*     inf	=    -inf
  -50.0	+    -inf	=    -inf
  -50.0	*    -inf	=     inf
    0.0	+   -50.0	=   -50.0
    0.0	*   -50.0	=    -0.0
    0.0	+     0.0	=     0.0
    0.0	*     0.0	=     0.0
    0.0	+    50.0	=    50.0
    0.0	*    50.0	=     0.0
    0.0	+     inf	=     inf
    0.0	*     inf	=     nan
    0.0	+    -inf	=    -inf
    0.0	*    -inf	=     nan
   50.0	+   -50.0	=     0.0
   50.0	*   -50.0	= -2500.0
   50.0	+     0.0	=    50.0
   50.0	*     0.0	=     0.0
   50.0	+    50.0	=   100.0
   50.0	*    50.0	=  2500.0
   50.0	+     inf	=     inf
   50.0	*     inf	=     inf
   50.0	+    -inf	=    -inf
   50.0	*    -inf	=    -inf
    inf	+   -50.0	=     inf
    inf	*   -50.0	=    -inf
    inf	+     0.0	=     inf
    inf	*     0.0	=     nan
    inf	+    50.0	=     inf
    inf	*    50.0	=     inf
    inf	+     inf	=     inf
    inf	*     inf	=     inf
    inf	+    -inf	=     nan
    inf	*    -inf	=    -inf
   -inf	+   -50.0	=    -inf
   -inf	*   -50.0	=     inf
   -inf	+     0.0	=    -inf
   -inf	*     0.0	=     nan
   -inf	+    50.0	=    -inf
   -inf	*    50.0	=    -inf
   -inf	+     inf	=     nan
   -inf	*     inf	=    -inf
   -inf	+    -inf	=    -inf
   -inf	*    -inf	=     inf

infty.c

#include <stdio.h>
#include <math.h>

int main(int argc, char **argv) {
    double a[5];
    a[0] = -50.0;
    a[1] = 0.0;
    a[2] = +50.0;
    a[3] = __builtin_inf();
    a[4] = -__builtin_inf();

    int i,j;
    for (i = 0; i < 5; i++)
        for (j = 0; j < 5; j++) {
            printf("%7.1f\t+ %7.1f\t= %7.1f\n", a[i], a[j], a[i]+a[j]);
            printf("%7.1f\t* %7.1f\t= %7.1f\n", a[i], a[j], a[i]*a[j]);
        }

    return 0;
}