From ee7c269301f84bd5c7c942900aaa2d96d17d886f Mon Sep 17 00:00:00 2001
From: David Li <li.davidm96@gmail.com>
Date: Sat, 4 Nov 2017 19:06:13 -0400
Subject: Parse binary operators with precedence

---
 src/taiga.lalrpop | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

(limited to 'src/taiga.lalrpop')

diff --git a/src/taiga.lalrpop b/src/taiga.lalrpop
index 08c3cd3..0182a04 100644
--- a/src/taiga.lalrpop
+++ b/src/taiga.lalrpop
@@ -8,7 +8,32 @@ pub Program: ast::Program = {
 };
 
 Expression: Box<ast::WithLocation<ast::Expression>> = {
+    <e1:Expression> "+" <e2:ExpressionMul> => Box::new(e1.join_map(*e2, |v1, v2| {
+        ast::Expression::BinOp(ast::BinOp::Add, Box::new(v1), Box::new(v2))
+    })),
+    <e1:Expression> "-" <e2:ExpressionMul> => Box::new(e1.join_map(*e2, |v1, v2| {
+        ast::Expression::BinOp(ast::BinOp::Sub, Box::new(v1), Box::new(v2))
+    })),
+    <ExpressionMul> => <>,
+};
+
+ExpressionMul: Box<ast::WithLocation<ast::Expression>> = {
+    <e1:ExpressionMul> "*" <e2:ExpressionBase> => Box::new(e1.join_map(*e2, |v1, v2| {
+        ast::Expression::BinOp(ast::BinOp::Mul, Box::new(v1), Box::new(v2))
+    })),
+    <e1:ExpressionMul> "/" <e2:ExpressionBase> => Box::new(e1.join_map(*e2, |v1, v2| {
+        ast::Expression::BinOp(ast::BinOp::Div, Box::new(v1), Box::new(v2))
+    })),
+    <e1:ExpressionMul> "//" <e2:ExpressionBase> => Box::new(e1.join_map(*e2, |v1, v2| {
+        ast::Expression::BinOp(ast::BinOp::FloorDiv, Box::new(v1), Box::new(v2))
+    })),
+    <ExpressionBase> => <>,
+};
+
+ExpressionBase: Box<ast::WithLocation<ast::Expression>> = {
     Num => Box::new(<>.map(|v| ast::Expression::Number(v))),
+    Spanned<r"nil"> => Box::new(<>.map(|v| ast::Expression::Nil)),
+    "(" <Expression> ")" => <>,
 };
 
 Num: WithLocation<u64> = <e: Spanned<r"[0-9]+">> => e.map(|v| u64::from_str(v).unwrap());
-- 
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