diff --git a/oden-script/src/parser.rs b/oden-script/src/parser.rs
index 262164f7..ce8c6bb7 100644
--- a/oden-script/src/parser.rs
+++ b/oden-script/src/parser.rs
@@ -47,10 +47,10 @@ pub enum BinaryOp {
     Or,
 }
 
-pub enum Expr {
-    Literal(Literal),
-    Unary(UnaryOp, ExprRef),
-    Binary(BinaryOp, ExprRef, ExprRef),
+pub enum Expr<'a> {
+    Literal(Literal, Token<'a>),
+    Unary(UnaryOp, Token<'a>, ExprRef),
+    Binary(BinaryOp, Token<'a>, ExprRef, ExprRef),
 }
 
 pub struct ExprRef(Option<usize>);
@@ -63,8 +63,7 @@ impl ExprRef {
 
 pub struct SyntaxTree<'a> {
     pub errors: Vec<SyntaxError>,
-    expressions: Vec<Expr>,
-    spans: Vec<(Option<Token<'a>>, Option<Token<'a>>)>,
+    expressions: Vec<Expr<'a>>,
 }
 
 impl<'a> SyntaxTree<'a> {
@@ -72,7 +71,6 @@ impl<'a> SyntaxTree<'a> {
         SyntaxTree {
             errors: Vec::new(),
             expressions: Vec::new(),
-            spans: Vec::new(),
         }
     }
 
@@ -80,51 +78,23 @@ impl<'a> SyntaxTree<'a> {
         self.errors.push(error);
     }
 
-    pub fn add_expr(
-        &mut self,
-        expr: Expr,
-        start: Option<Token<'a>>,
-        end: Option<Token<'a>>,
-    ) -> ExprRef {
+    pub fn add_expr(&mut self, expr: Expr<'a>) -> ExprRef {
         let index = self.expressions.len();
         self.expressions.push(expr);
-        self.spans.push((start, end));
         ExprRef(Some(index))
     }
 
-    pub fn span(&self, expr: &ExprRef) -> (Option<Token<'a>>, Option<Token<'a>>) {
-        if let ExprRef(Some(idx)) = expr {
-            let (start, end) = &self.spans[*idx];
-            (start.clone(), end.clone())
-        } else {
-            (None, None)
-        }
-    }
-
     pub fn dump_expr(&self, expr: &ExprRef) -> String {
         match expr.0 {
             Some(idx) => {
                 let expr = &self.expressions[idx];
                 match expr {
-                    Expr::Literal(lit) => match lit {
-                        Literal::Float64(f) => f.to_string(),
-                    },
-                    Expr::Unary(op, e) => {
-                        let op = match op {
-                            UnaryOp::Negate => "-",
-                        };
-                        format!("({op} {})", self.dump_expr(e))
+                    Expr::Literal(_, tok) => tok.to_string(),
+                    Expr::Unary(_, tok, e) => {
+                        format!("({tok} {})", self.dump_expr(e))
                     }
-                    Expr::Binary(op, l, r) => {
-                        let op = match op {
-                            BinaryOp::Add => "+",
-                            BinaryOp::Subtract => "-",
-                            BinaryOp::Mutiply => "*",
-                            BinaryOp::Divide => "/",
-                            BinaryOp::And => "and",
-                            BinaryOp::Or => "or",
-                        };
-                        format!("({op} {} {})", self.dump_expr(l), self.dump_expr(r))
+                    Expr::Binary(_, tok, l, r) => {
+                        format!("({tok} {} {})", self.dump_expr(l), self.dump_expr(r))
                     }
                 }
             }
@@ -263,11 +233,7 @@ impl<'a> Parser<'a> {
             }
         };
 
-        self.tree.add_expr(
-            Expr::Literal(literal),
-            Some(token.clone()),
-            Some(token.clone()),
-        )
+        self.tree.add_expr(Expr::Literal(literal, token.clone()))
     }
 
     fn grouping(&mut self) -> ExprRef {
@@ -288,8 +254,7 @@ impl<'a> Parser<'a> {
             _ => panic!("unsuitable unary: {:?}: no op", kind),
         };
 
-        self.tree
-            .add_expr(Expr::Unary(op, expr), Some(token), self.previous.clone())
+        self.tree.add_expr(Expr::Unary(op, token, expr))
     }
 
     fn binary(&mut self, power: u8, left: ExprRef) -> ExprRef {
@@ -304,12 +269,7 @@ impl<'a> Parser<'a> {
             _ => panic!("unsuitable binary: {:?}: no op", self.previous),
         };
         let right = self.expression_with_power(power + 1);
-
-        let (left_start, _) = self.tree.span(&left);
-        let (_, right_end) = self.tree.span(&right);
-
-        self.tree
-            .add_expr(Expr::Binary(op, left, right), left_start, right_end)
+        self.tree.add_expr(Expr::Binary(op, token, left, right))
     }
 
     fn advance(&mut self) {
@@ -318,7 +278,7 @@ impl<'a> Parser<'a> {
             self.current = self.tokens.next();
             match &self.current {
                 Some(token) if token.kind() == TokenKind::Error => {
-                    self.error_at_current(token.clone())
+                    self.error_at_current(token.to_string())
                 }
                 _ => break,
             }
diff --git a/oden-script/src/tokens.rs b/oden-script/src/tokens.rs
index 2a09336e..c989dab9 100644
--- a/oden-script/src/tokens.rs
+++ b/oden-script/src/tokens.rs
@@ -89,9 +89,9 @@ impl<'a> Token<'a> {
     }
 }
 
-impl<'a> Into<String> for Token<'a> {
-    fn into(self) -> String {
-        self.as_str().to_string()
+impl<'a> std::fmt::Display for Token<'a> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.as_str())
     }
 }