Rust: add step3_env

1 files changed, 44 insertions, 0 deletions

diff --git a/rust/src/env.rs b/rust/src/env.rs
new file mode 100644
index 0000000..9c98f23
--- /dev/null
+++ b/rust/src/env.rs
@@ -0,0 +1,44 @@
+use std::rc::Rc;
+use std::cell::RefCell;
+use std::collections::HashMap;
+
+use types::{MalVal,MalRet,Nil};
+
+struct EnvType {
+    data: HashMap<String,MalVal>,
+    outer: Option<Env>,
+}
+
+pub type Env = Rc<RefCell<EnvType>>;
+
+pub fn env_new(outer: Option<Env>) -> Env {
+    Rc::new(RefCell::new(EnvType{data: HashMap::new(), outer: outer}))
+}
+
+pub fn env_find(env: Env, key: String) -> Option<Env> {
+    if env.borrow().data.contains_key(&key) {
+        Some(env)
+    } else {
+        match env.borrow().outer {
+            Some(ref e) => env_find(e.clone(), key),
+            None => None,
+        }
+    }
+}
+
+pub fn env_set(env: &Env, key: String, val: MalVal) {
+    env.borrow_mut().data.insert(key, val.clone());
+}
+
+pub fn env_get(env: Env, key: String) -> MalRet {
+    match env_find(env, key.clone()) {
+        Some(e) => {
+            match e.borrow().data.find_copy(&key) {
+                Some(v) => Ok(v),
+                None => Ok(Rc::new(Nil)),
+            }
+        },
+        None    => Ok(Rc::new(Nil)),
+    }
+}
+