my_fucking_datatype

#include <stdio.h>
#include <stdlib.h>

typedef struct my_fucking_datatype {
        int is_int;
        union  {
                int int_val;
                float float_val;
        };
} my_fucking_datatype_t;

#define set_value(data, v)              \
do {                                    \
        if (__builtin_types_compatible_p(typeof (v), int)) { \
                (data)->is_int = 1;                          \
                (data)->int_val = v;                         \
        } else if (__builtin_types_compatible_p(typeof (v), float)) { \
                (data)->is_int = 0;                          \
                (data)->float_val = v;                       \
        } else abort();                                       \
} while(0)

#define is_int(data) ((data)->is_int == 1)
#define is_float(data)  !is_int(data)

int main(void)
{
        my_fucking_datatype_t data;
        int sample_int_value = 5;
        float sample_float_value = 7.14;

        set_value(&data, sample_int_value);
        if (is_int(&data))
                printf("currently holds an int value\n");

        set_value(&data, sample_float_value);
        if (!is_int(&data))
                printf("currently holds a float value\n");


        return 0;
}