Lex and parse parentheses

2 files changed, 10 insertions, 0 deletions

diff --git a/src/lexer.js b/src/lexer.js
index fd347c6..f559816 100644
--- a/src/lexer.js
+++ b/src/lexer.js
@@ -22,6 +22,8 @@ newValueLexeme('constant', '\\d+', Number)
 newLexemeType('d', 'd')
 newLexemeType('+', '\\+')
 newLexemeType('-', '-')
+newLexemeType('(', '\\(')
+newLexemeType(')', '\\)')
 newSkippableLexeme('whitespace', '\\s+')
 
 const lex = (expressionString) => {
diff --git a/src/parser.js b/src/parser.js
index 6c39c77..9f2c6ac 100644
--- a/src/parser.js
+++ b/src/parser.js
@@ -16,6 +16,14 @@ newSymbol('constant', function() {
   return { type: 'constant', value: this.value }
 })
 
+newSymbol('(', function(parser) {
+  const value = parser.expression(1)
+  parser.match(')')
+  return value
+})
+
+newSymbol(')')
+
 newSymbol('d', null, 30, (left, parser) => {
   return {
     type: 'd',