diff --git a/src/lib/expr.test.ts b/src/lib/expr.test.ts
index 3b7b4ce..31b4714 100644
--- a/src/lib/expr.test.ts
+++ b/src/lib/expr.test.ts
@@ -5,10 +5,10 @@ describe("expr", () => {
   test.each([
     ["1", "1"],
     ["1 + 2", "3"],
-    // ["1 - 2", "-1"],
-    // ["1 * 2", "2"],
-    // ["1 / 2", "0.5"],
-    // ["1 // 2", "0"],
+    ["1 - 2", "-1"],
+    ["1 * 2", "2"],
+    ["1 / 2", "0.5"],
+    ["1 // 2", "0"],
     // TODO: operator precedence
     // TODO: parentheses
     // TODO; eror reporting
diff --git a/src/lib/expr.ts b/src/lib/expr.ts
index 9926251..880ee2a 100644
--- a/src/lib/expr.ts
+++ b/src/lib/expr.ts
@@ -66,6 +66,32 @@ const Operators: TokenHandler[] = [
     parse: ({ value: left }, matched, parser) =>
       map(parser.parseSubExpression(11), (right) => ({ value: left + right })),
   },
+  {
+    leftBindingPower: 10,
+    token: MINUS_TOKEN,
+    parse: ({ value: left }, matched, parser) =>
+      map(parser.parseSubExpression(11), (right) => ({ value: left - right })),
+  },
+  {
+    leftBindingPower: 20,
+    token: TIMES_TOKEN,
+    parse: ({ value: left }, matched, parser) =>
+      map(parser.parseSubExpression(11), (right) => ({ value: left * right })),
+  },
+  {
+    leftBindingPower: 20,
+    token: FLOOR_TOKEN,
+    parse: ({ value: left }, matched, parser) =>
+      map(parser.parseSubExpression(11), (right) => ({
+        value: Math.floor(left / right),
+      })),
+  },
+  {
+    leftBindingPower: 20,
+    token: DIV_TOKEN,
+    parse: ({ value: left }, matched, parser) =>
+      map(parser.parseSubExpression(11), (right) => ({ value: left / right })),
+  },
 ];
 
 const ZERO = { value: 0 };