switch.c

if (rtn == RESULT_A || rtn == RESULT_B || rtn == RESULT_C || rtn == RESULT_D) {
    Do1();
} else {
    Do2();
}

switch (rtn) {
case RESULT_A:
case RESULT_B:
case RESULT_C:
case RESULT_D:
    Do1();
    break;
default:
    Do2();
    break;
}

// Compile: gcc -c -Wall -Wextra switch.c

void Do1(void);
void Do2(void);

enum { RESULT_A, RESULT_B, RESULT_C, RESULT_D };

void branch1(int rtn) {
if (rtn == RESULT_A || rtn == RESULT_B || rtn == RESULT_C || rtn == RESULT_D) {
Do1();
} else {
Do2();
}
}

void branch2(int rtn) {
switch (rtn) {
case RESULT_A:
case RESULT_B:
case RESULT_C:
case RESULT_D:
Do1();
break;
default:
Do2();
break;
}
}