Plus and multiply

This commit is contained in:
greg 2017-12-25 23:10:16 -08:00
parent c35b684bdd
commit 339e3464e3

View File

@ -217,9 +217,28 @@ impl EvaluatorState {
use self::Sexp::*;
use self::BuiltinFn::*;
Ok(match op {
Plus => match operands {
Cons(box NumberAtom(l), box Cons(box NumberAtom(r), box Nil)) => NumberAtom(l + r),
_ => return Err(format!("Bad arguments for +")),
Plus | Mult => {
let mut result = match op { Plus => 0, Mult => 1, _ => unreachable!() };
let mut operand = &operands;
loop {
match operand {
&Nil => break,
&Cons(ref l, ref r) => {
if let NumberAtom(ref n) = **l {
if let Plus = op {
result += n;
} else if let Mult = op {
result *= n;
}
operand = r as &Sexp;
} else {
return Err(format!("Bad operand"));
}
},
_ => return Err(format!("Bad operands list"))
}
}
NumberAtom(result)
},
_ => return Err(format!("Not implemented")),
})