#include <stdio.h>
#include <stdlib.h>
 
typedef int (*fx_p)(int, int);
 
int testadd(int a, int b) { return a+b; }
int testsub(int a, int b) { return a-b; }
int testmul(int a, int b) { return a*b; }
int testdiv(int a, int b) { return a/b; }
 
fx_p getfx(int n) {
    switch (n) {
        default: return testadd;
        case 4: case 5: case 6: return testsub;
        case 7: case 8: return testmul;
        case 9: return testdiv;
    }
}
 
int main(void) {
    // missing srand on purpose
	for (int k = 0; k < 20; k++) printf("%d\n", getfx(rand() % 10)(42, 10));
	return 0;
}
 

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