The switch statement

Conditionals such as the switch statement use the same logic as shown:

switch (age) {
case 18:
  can_drink = false;
  can_code = true;
  break;
case 21: 
  can_drink = true;
  can_code = true;
  break;
default: 
  can_drink = false;
}

Let's suppose rax represents the age, rbx represents can_drink, and rdx represents  can_code. The preceding example will translate into the following assembly instructions (simplified to express the basic idea):

cmp rax, 18
je CASE_18
cmp rax, 21
je CASE_21
je CASE_DEFAULT
CASE_18:
  mov rbx, 0; cannot drink
  mov rdx, 1; can code
  jmp BEYOND_SWITCH; break 
CASE_21:
  mov rbx, 1
  mov rdx, 1
  jmp BEYOND_SWITCH
CASE_DEFAULT:
  mov rbx, 0
BEYOND_SWITCH:
  ; ....

Each break statement translates into jumping to the BEYOND_SWITCH label, so if we forget the break keyword, for example, in the case where age is 18, the execution will reach through  CASE_21 as well. That's why you should not forget the break statement.

Let's find a way to avoid using conditionals in the source, both to make the code shorter and possibly faster. We will use function pointers.