typedef union {
    int i;
    float f;
} ambivalent_union;

//My plan is for this macro to work for both ints and floats.
#define MY_MACRO( some_expression ) \
    ambivalent_union u = (ambivalent_union)(some_expression); \
    printf("If the expression returned a float, it would be %f", ambivalent_union.f); \
    printf("If the expression returned an int, it would be %d", ambivalent_union.i);