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Evaluate simple binops 

Woo this is kind of a neat milestone! I can now compute with this
language!
This commit is contained in:
greg 2015-08-07 01:50:31 -07:00
parent be8c8b3343
commit 50c5dbe96d
1 changed files with 32 additions and 0 deletions
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32
src/evaluate.rs
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@ -54,6 +54,11 @@ fn reduce(evr: EvalResult) -> EvalResult {
let (ast, mut env) = evr;
match ast {
BinOp(op, lhs, rhs) => {
let result: AST = reduce_binop(*op, *lhs, *rhs);
(result, env)
},
Name(name) => {
let result = match env.lookup_binding(&name) {
Some(binding) => match binding {
@ -92,3 +97,30 @@ fn reduce(evr: EvalResult) -> EvalResult {
other_ast => (other_ast, env)
}
}
fn reduce_binop(op: AST, lhs: AST, rhs: AST) -> AST {
macro_rules! LangBool {
(true) => [Name("true".to_string())];
(false) => [Name("false".to_string())];
}
match (lhs, rhs) {
(Number(l), Number(r)) => match op {
Name(ref s) if *s == "+" => Number(l + r),
Name(ref s) if *s == "-" => Number(l - r),
Name(ref s) if *s == "*" => Number(l * r),
Name(ref s) if *s == "/" => if r == 0.0 { Null } else { Number(l / r) },
Name(ref s) if *s == "==" => if l == r { LangBool!(true) } else { LangBool!(false) },
Name(ref s) if *s == ">" => if l > r { LangBool!(true) } else { LangBool!(false) },
Name(ref s) if *s == "<" => if l < r { LangBool!(true) } else { LangBool!(false) },
_ => Null
},
(LangString(s1), LangString(s2)) => match op {
Name(ref s) if *s == "+" => LangString(format!("{}{}", s1, s2)),
_ => Null
},
_ => Null
}
}