add dumb comments
@@ -182,6 +182,8 @@ fn execute_query_instr<'a, 'b: 'a>(&'a mut self, instr: &'b QueryInstruction) {
match instr {
&QueryInstruction::Call(ref name, arity) => {
// why is Option<&T> not Deref?!?!?
+ // is it because if the value is None, there's nothing to
+ // dereference?
let compiled_fact_index =
self.code_dir.get(&(name.clone(), arity))
.map(|index| *index);
