Pretty-print evaluated AST nodes

src/eval.rs

@@ -73,7 +73,7 @@ impl Evaluator {
             }
         }
 
-        format!("{:?}", node) //TODO make better
+        format!("{}", node) //TODO make better
     }
 
     fn step(&mut self, node: ASTNode) -> ASTNode {

src/parser.rs

@@ -1,3 +1,4 @@
+use std::fmt;
 use tokenizer::{Token, Kw, Op};
 
 /* Grammar
@@ -45,6 +46,28 @@ pub enum Expression {
     Call(String, Vec<Expression>),
 }
 
+impl fmt::Display for ASTNode {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use self::ASTNode::*;
+        match self {
+            &ExprNode(ref expr) => write!(f, "{}", expr),
+            &FuncNode(_) => write!(f, "UNIMPLEMENTED"),
+        }
+    }
+}
+
+impl fmt::Display for Expression {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        use self::Expression::*;
+        match self {
+            &Null => write!(f, "null"),
+            &StringLiteral(ref s) => write!(f, "\"{}\"", s),
+            &Number(n) => write!(f, "{}", n),
+            _ => write!(f, "UNIMPLEMENTED"),
+        }
+    }
+}
+
 pub type AST = Vec<ASTNode>;
 
 type Precedence = u8;