https://github.com/akkartik/mu/blob/master/apps/factorial.mu
 1 fn main -> result/ebx: int {
 2   var tmp/eax: int <- factorial 5
 3   result <- copy tmp
 4 }
 5 
 6 fn factorial n: int -> result/eax: int {
 7   compare n 1
 8   {
 9     break-if->
10     result <- copy 1
11   }
12   {
13     break-if-<=
14     var tmp/ecx: int <- copy n
15     tmp <- decrement
16     result <- factorial tmp
17     result <- multiply n
18   }
19 }