Environment persistent across repl loop

src/evaluate.rs

@@ -35,17 +35,19 @@ impl Environment {
     }
 }
 
-pub fn evaluate(ast: AST, env: Environment) -> String {
+pub fn evaluate(ast: AST, env: Environment) -> (String, Environment) {
 
     let (mut reduced_ast, final_env) = reduce((ast, env));
 
-    match reduced_ast {
+    let output = match reduced_ast {
         DoNothing => "".to_string(),
-        Number(n) => return format!("{}", n),
-        LangString(s) => return format!("\"{}\"", s),
+        Number(n) => format!("{}", n),
+        LangString(s) => format!("\"{}\"", s),
         Null => "null".to_string(),
-        _ => return "not implemented".to_string()
-    }
+        _ => "not implemented".to_string()
+    };
+
+    (output, final_env)
 }
 
 fn reduce(evr: EvalResult) -> EvalResult {

src/main.rs

@@ -21,6 +21,7 @@ fn repl() {
     let stdin = io::stdin();
     let mut stdout = io::stdout();
     let mut buf = String::with_capacity(20);
+    let mut env = Environment::new();
     loop {
         buf.clear();
         print!(">> ");
@@ -44,9 +45,9 @@ fn repl() {
                     ParseResult::Ok(ast) => {
                         println!("AST: {:?}", ast);
 
-                        let env = Environment::new();
-                        let eval = evaluate(ast, env);
+                        let (eval, new_env) = evaluate(ast, env);
                         println!("{}", eval);
+                        env = new_env;
                     },
                     ParseResult::Err(err) => println!("Error: {}", err)
                 }