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Add support for multiple frames

This commit is contained in:
greg 2016-01-23 20:49:16 -08:00
parent dcde5d6018
commit 77f72806be
1 changed files with 18 additions and 4 deletions
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22
src/eval.rs
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@ -26,12 +26,16 @@ impl Funcmap {
pub struct Evaluator {
varmap: Varmap,
funcmap: Funcmap,
frames: Vec<Varmap>,
}
impl Evaluator {
pub fn new() -> Evaluator {
Evaluator { varmap: Varmap::new(), funcmap: Funcmap::new() }
Evaluator { varmap: Varmap::new(),
funcmap: Funcmap::new(),
frames: Vec::new(),
}
}
pub fn run(&mut self, ast: AST) -> Vec<String> {
@ -44,8 +48,18 @@ impl Evaluator {
self.varmap.map.insert(var, value);
}
fn lookup_binding(&mut self, var: String) -> Option<&Expression> {
self.varmap.map.get(&var)
fn lookup_binding(&mut self, var: String) -> Option<Expression> {
self.varmap.map.get(&var).map(|expr| expr.clone())
.or_else(|| {
for frame in self.frames.iter() {
match frame.map.get(&var) {
None => (),
Some(expr) => return Some(expr.clone()),
}
}
None
})
}
fn add_function(&mut self, name: String, function: Function) {
@ -126,7 +140,7 @@ impl Evaluator {
Variable(var) => {
match self.lookup_binding(var) {
None => Null,
Some(expr) => expr.clone()
Some(expr) => expr,
}
},
BinExp(op, box left, box right) => {