feat: simple functions

src/vm/env.rs

@@ -8,6 +8,11 @@ pub struct Env {
     map: HashTrieMapSync<Symbol, Value>,
 }
 
+#[derive(Debug, Clone)]
+pub struct LockedEnv {
+    map: HashTrieMapSync<Symbol, Value>
+}
+
 impl Env {
     pub fn empty() -> Env {
         Env {
@@ -16,20 +21,19 @@ impl Env {
         }
     }
 
-    pub fn lookup(&self, symbol: Symbol) -> Value {
-        if let Some(value) = self.map.get(&symbol) {
-            value.clone()
-        } else {
-            let last = self.last.as_ref().unwrap();
-            last.lookup(symbol)
-        }
+    pub fn lookup(&self, symbol: Symbol) -> Option<Value> {
+        self.map.get(&symbol).cloned()
     }
 
     pub fn insert(&mut self, symbol: Symbol, value: Value) {
         self.map.insert_mut(symbol, value);
     }
 
-    pub fn enter(&mut self, map: HashTrieMapSync<Symbol, Value>) {
+    pub fn enter(&mut self, new: HashTrieMapSync<Symbol, Value>) {
+        let mut map = self.map.clone();
+        for (k, v) in new.iter() {
+            map.insert_mut(k.clone(), v.clone());
+        }
         let last = std::mem::replace(self, Env { last: None, map });
         self.last = Some(Box::new(last));
     }
@@ -37,6 +41,23 @@ impl Env {
     pub fn leave(&mut self) {
         let last = std::mem::replace(&mut self.last, None).unwrap();
         let _ = std::mem::replace(&mut self.last, last.last);
-        self.map = last.map.clone();
+        self.map = last.map;
+    }
+
+    pub fn locked(&self) -> LockedEnv {
+        LockedEnv { map: self.map.clone() }
+    }
+}
+
+impl LockedEnv {
+    pub fn lookup(&self, symbol: Symbol) -> Option<Value> {
+        self.map.get(&symbol).cloned()
+    }
+
+    pub fn unlocked(self) -> Env {
+        Env {
+            map: self.map,
+            last: None
+        }
     }
 }