gen.c

#include <stdio.h>
#define print(X) _Generic((X), \
                 double: printf("%f\n", X),\
                 int: printf("%d\n", X),\
		 char: printf("%c\n", X))
                 
int main (void) {
    int x = 42;
    double z = 11.0;
    print(x);
    print(z);
    print((char)'a');
}