don't repeat l/rhs in eval

src/eval.rs

@@ -20,12 +20,16 @@ impl Evaluator {
                 }
             },
             Expr::Binary { op, left, right } => {
+                let lhs = self.eval_expr(*left);
+                let rhs = self.eval_expr(*right);
+                
                 match op {
-                    BinaryOp::Add => self.eval_expr(*left) + self.eval_expr(*right),
+                    BinaryOp::Add => lhs + rhs,
-                    BinaryOp::Sub => self.eval_expr(*left) - self.eval_expr(*right),
+                    BinaryOp::Sub => lhs - rhs,
-                    BinaryOp::Mul => self.eval_expr(*left) * self.eval_expr(*right),
+                    BinaryOp::Mul => lhs * rhs,
-                    BinaryOp::Div => self.eval_expr(*left) / self.eval_expr(*right),
+                    BinaryOp::Div => lhs / rhs,
-                    BinaryOp::Mod => self.eval_expr(*left) % self.eval_expr(*right)
+                    BinaryOp::Mod => lhs % rhs,
+                    BinaryOp::Exp => lhs.pow(rhs as u32) // probably shouldn't cast like that
                 }
             },
             expr => panic!("can't eval expression: {expr:?}")

src/expr.rs

@@ -4,7 +4,8 @@ pub enum BinaryOp {
     Sub,
     Mul,
     Div,
-    Mod
+    Mod,
+    Exp
 }
 
 #[derive(Debug, Clone)]
@@ -14,14 +15,15 @@ pub enum UnaryOp {
 
 pub fn prefix_bp(op: &UnaryOp) -> u8 {
     match op {
-        UnaryOp::Neg => 5
+        UnaryOp::Neg => 7
     }
 }
 
 pub fn infix_bp(op: &BinaryOp) -> (u8, u8) {
     match op {
         BinaryOp::Add | BinaryOp::Sub => (1, 2),
-        BinaryOp::Mul | BinaryOp::Div | BinaryOp::Mod => (3, 4)
+        BinaryOp::Mul | BinaryOp::Div | BinaryOp::Mod => (3, 4),
+        BinaryOp::Exp => (5, 6)
     }
 }
 

src/lexer.rs

@@ -59,6 +59,7 @@ impl Lexer {
             Some(b'*') => {self.advance(); Some(Token::Asterisk)},
             Some(b'/') => {self.advance(); Some(Token::Slash)},
             Some(b'%') => {self.advance(); Some(Token::Percent)},
+            Some(b'^') => {self.advance(); Some(Token::Caret)},
 
             Some(b'(') => {self.advance(); Some(Token::LParen)},
             Some(b')') => {self.advance(); Some(Token::RParen)},

src/parser.rs

@@ -69,6 +69,7 @@ impl Parser {
                 Some(Token::Asterisk) => BinaryOp::Mul,
                 Some(Token::Slash) => BinaryOp::Div,
                 Some(Token::Percent) => BinaryOp::Mod,
+                Some(Token::Caret) => BinaryOp::Exp,
                 _ => break
             };
 

src/token.rs

@@ -9,6 +9,7 @@ pub enum Token {
     Asterisk,
     Slash,
     Percent,
+    Caret,
 
     // Parentheses
     LParen,