Implement while-reduction

src/evaluate.rs

@@ -1,4 +1,5 @@
 use std::collections::HashMap;
+use std::clone::Clone;
 
 use parser::AST;
 use parser::AST::*;
@@ -67,6 +68,17 @@ fn reduce(evr: EvalResult) -> EvalResult {
             }
         },
 
+        WhileStatement(condition, body) => {
+            let (continue_loop, env) = reduce((*condition.clone(), env));
+            match continue_loop {
+                Null => (DoNothing, env),
+                _ => {
+                    let (_, new_env) = reduce((*body.clone(), env));
+                    reduce((WhileStatement(condition, body), new_env))
+                }
+            }
+        },
+
         BinOp(op, lhs, rhs) => {
             let (reduced_lhs, new_env) = reduce((*lhs, env));
             let (reduced_rhs, new_env2) = reduce((*rhs, new_env));

src/parser.rs

@@ -4,7 +4,7 @@ use std::iter::Peekable;
 use tokenizer::{Token, Kw};
 use tokenizer::Token::*;
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub enum AST {
     Null,
     Name(String),