regexp: interpret all Go characer escapes \a \b \f \n \r \t \v

R=rsc
CC=golang-dev
https://golang.org/cl/2042044

src/pkg/regexp/find_test.go

@@ -57,6 +57,8 @@ var findTests = []FindTest{
 	FindTest{`(([^xyz]*)(d))`, "abcd", build(1, 0, 4, 0, 4, 0, 3, 3, 4)},
 	FindTest{`((a|b|c)*(d))`, "abcd", build(1, 0, 4, 0, 4, 2, 3, 3, 4)},
 	FindTest{`(((a|b|c)*)(d))`, "abcd", build(1, 0, 4, 0, 4, 0, 3, 2, 3, 3, 4)},
+	FindTest{`\a\b\f\n\r\t\v`, "\a\b\f\n\r\t\v", build(1, 0, 7)},
+	FindTest{`[\a\b\f\n\r\t\v]+`, "\a\b\f\n\r\t\v", build(1, 0, 7)},
 
 	FindTest{`a*(|(b))c*`, "aacc", build(1, 0, 4, 2, 2, -1, -1)},
 	FindTest{`(.*).*`, "ab", build(1, 0, 2, 0, 2)},

src/pkg/regexp/regexp.go

@@ -22,7 +22,8 @@
 //		character [ '-' character ]
 //
 // All characters are UTF-8-encoded code points.  Backslashes escape special
-// characters, including inside character classes.
+// characters, including inside character classes.  The standard Go character
+// escapes are also recognized: \a \b \f \n \r \t \v.
 //
 // There are 16 methods of Regexp that match a regular expression and identify
 // the matched text.  Their names are matched by this regular expression:
@@ -353,6 +354,18 @@ func ispunct(c int) bool {
 	return false
 }
 
+var escapes = []byte("abfnrtv")
+var escaped = []byte("\a\b\f\n\r\t\v")
+
+func escape(c int) int {
+	for i, b := range escapes {
+		if int(b) == c {
+			return i
+		}
+	}
+	return -1
+}
+
 func (p *parser) charClass() instr {
 	cc := newCharClass()
 	if p.c() == '^' {
@@ -388,10 +401,10 @@ func (p *parser) charClass() instr {
 			switch {
 			case c == endOfFile:
 				p.error(ErrExtraneousBackslash)
-			case c == 'n':
-				c = '\n'
 			case ispunct(c):
 				// c is as delivered
+			case escape(c) >= 0:
+				c = int(escaped[escape(c)])
 			default:
 				p.error(ErrBadBackslash)
 			}
@@ -483,10 +496,10 @@ func (p *parser) term() (start, end instr) {
 		switch {
 		case c == endOfFile:
 			p.error(ErrExtraneousBackslash)
-		case c == 'n':
-			c = '\n'
 		case ispunct(c):
 			// c is as delivered
+		case escape(c) >= 0:
+			c = int(escaped[escape(c)])
 		default:
 			p.error(ErrBadBackslash)
 		}