Add arithmetic expressions

editors/tree-sitter-decodal/grammar.js

@@ -2,6 +2,9 @@ const PREC = {
   DEFAULT: 1,
   PATCH: 2,
   AND: 3,
+  ADD: 4,
+  MUL: 5,
+  UNARY: 6,
   CALL: 7,
   PATH: 8,
 };
@@ -52,6 +55,7 @@ module.exports = grammar({
       $.parenthesized_expression,
       $.call_expression,
       $.path_expression,
+      $.unary_expression,
       $.binary_expression,
       $.default_expression,
     ),
@@ -161,10 +165,25 @@ module.exports = grammar({
 
     comparison_constraint: $ => prec(6, seq(
       field('operator', choice('>', '>=', '<', '<=')),
-      field('value', choice($.integer, $.float)),
+      field('value', $._expression),
+    )),
+
+    unary_expression: $ => prec(PREC.UNARY, seq(
+      field('operator', '-'),
+      field('operand', $._expression),
     )),
 
     binary_expression: $ => choice(
+      prec.left(PREC.ADD, seq(
+        field('left', $._expression),
+        field('operator', choice('+', '-')),
+        field('right', $._expression),
+      )),
+      prec.left(PREC.MUL, seq(
+        field('left', $._expression),
+        field('operator', choice('*', '/')),
+        field('right', $._expression),
+      )),
       prec.left(PREC.AND, seq(
         field('left', $._expression),
         field('operator', '&'),