From 0255587e95af39f757d227e477792ff2f3a92bd8 Mon Sep 17 00:00:00 2001
From: Fatih Arslan <ftharsln@gmail.com>
Date: Sun, 4 Oct 2015 23:47:06 +0300
Subject: [PATCH] scnaner: implement scanning hexadecimal numbers

---
 scanner/scanner.go      | 30 ++++++++++++++++++++++++++++--
 scanner/scanner_test.go | 24 ++++++++++++------------
 2 files changed, 40 insertions(+), 14 deletions(-)

diff --git a/scanner/scanner.go b/scanner/scanner.go
index fda5265..337691a 100644
--- a/scanner/scanner.go
+++ b/scanner/scanner.go
@@ -132,8 +132,13 @@ func (s *Scanner) Scan() (tok token.Token) {
 func (s *Scanner) scanNumber(ch rune) token.Token {
 	if ch == '0' {
 		// check hexadecimal or float
-		// ch = s.next()
-		// return token.ILLEGAL
+		ch = s.next()
+		if ch == 'x' || ch == 'X' {
+			ch = s.next()
+			s.scanHexadecimal(ch)
+			return token.NUMBER
+		}
+
 	}
 
 	s.scanMantissa(ch)
@@ -147,6 +152,23 @@ func (s *Scanner) scanMantissa(ch rune) {
 	s.unread()
 }
 
+func (s *Scanner) scanHexadecimal(ch rune) {
+	found := false
+
+	// after "0x" or "0X"
+	for isHexadecimal(ch) {
+		ch = s.next()
+		found = true
+	}
+
+	if !found {
+		// only scanned "0x" or "0X"
+		s.err("illegal hexadecimal number")
+	}
+
+	s.unread()
+}
+
 // scanString scans a quoted string
 func (s *Scanner) scanString() {
 	for {
@@ -268,6 +290,10 @@ func isDecimal(ch rune) bool {
 	return '0' <= ch && ch <= '9'
 }
 
+func isHexadecimal(ch rune) bool {
+	return '0' <= ch && ch <= '9' || 'a' <= ch && ch <= 'f' || 'A' <= ch && ch <= 'F'
+}
+
 // isWhitespace returns true if the rune is a space, tab, newline or carriage return
 func isWhitespace(ch rune) bool {
 	return ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r'
diff --git a/scanner/scanner_test.go b/scanner/scanner_test.go
index 8ce08c0..4df11ea 100644
--- a/scanner/scanner_test.go
+++ b/scanner/scanner_test.go
@@ -111,18 +111,18 @@ func TestNumber(t *testing.T) {
 		{token.NUMBER, "07"},
 		{token.NUMBER, "042"},
 		{token.NUMBER, "01234567"},
-		// {token.NUMBER, "0x0"},
-		// {token.NUMBER, "0x1"},
-		// {token.NUMBER, "0xf"},
-		// {token.NUMBER, "0x42"},
-		// {token.NUMBER, "0x123456789abcDEF"},
-		// {token.NUMBER, "0x" + f100},
-		// {token.NUMBER, "0X0"},
-		// {token.NUMBER, "0X1"},
-		// {token.NUMBER, "0XF"},
-		// {token.NUMBER, "0X42"},
-		// {token.NUMBER, "0X123456789abcDEF"},
-		// {token.NUMBER, "0X" + f100},
+		{token.NUMBER, "0x0"},
+		{token.NUMBER, "0x1"},
+		{token.NUMBER, "0xf"},
+		{token.NUMBER, "0x42"},
+		{token.NUMBER, "0x123456789abcDEF"},
+		{token.NUMBER, "0x" + f100},
+		{token.NUMBER, "0X0"},
+		{token.NUMBER, "0X1"},
+		{token.NUMBER, "0XF"},
+		{token.NUMBER, "0X42"},
+		{token.NUMBER, "0X123456789abcDEF"},
+		{token.NUMBER, "0X" + f100},
 		// {token.FLOAT, "0."},
 		// {token.FLOAT, "1."},
 		// {token.FLOAT, "42."},