regexp: add examples

Update golang#4125

R=minux.ma, rsc
CC=golang-dev
https://golang.org/cl/6847107

Author: vdobler

src/pkg/regexp/example_test.go

@@ -20,3 +20,125 @@ func Example() {
 	// false
 	// false
 }
+
+func ExampleMatchString() {
+	matched, err := regexp.MatchString("foo.*", "seafood")
+	fmt.Println(matched, err)
+	matched, err = regexp.MatchString("bar.*", "seafood")
+	fmt.Println(matched, err)
+	matched, err = regexp.MatchString("a(b", "seafood")
+	fmt.Println(matched, err)
+	// Output:
+	// true <nil>
+	// false <nil>
+	// false error parsing regexp: missing closing ): `a(b`
+}
+
+func ExampleRegexp_FindString() {
+	re := regexp.MustCompile("fo.?")
+	fmt.Printf("%q\n", re.FindString("seafood"))
+	fmt.Printf("%q\n", re.FindString("meat"))
+	// Output:
+	// "foo"
+	// ""
+}
+
+func ExampleRegexp_FindStringIndex() {
+	re := regexp.MustCompile("ab?")
+	fmt.Println(re.FindStringIndex("tablett"))
+	fmt.Println(re.FindStringIndex("foo") == nil)
+	// Output:
+	// [1 3]
+	// true
+}
+
+func ExampleRegexp_FindStringSubmatch() {
+	re := regexp.MustCompile("a(x*)b(y|z)c")
+	fmt.Printf("%q\n", re.FindStringSubmatch("-axxxbyc-"))
+	fmt.Printf("%q\n", re.FindStringSubmatch("-abzc-"))
+	// Output:
+	// ["axxxbyc" "xxx" "y"]
+	// ["abzc" "" "z"]
+}
+
+func ExampleRegexp_FindAllString() {
+	re := regexp.MustCompile("a.")
+	fmt.Println(re.FindAllString("paranormal", -1))
+	fmt.Println(re.FindAllString("paranormal", 2))
+	fmt.Println(re.FindAllString("graal", -1))
+	fmt.Println(re.FindAllString("none", -1))
+	// Output:
+	// [ar an al]
+	// [ar an]
+	// [aa]
+	// []
+}
+
+func ExampleRegexp_FindAllStringSubmatch() {
+	re := regexp.MustCompile("a(x*)b")
+	fmt.Printf("%q\n", re.FindAllStringSubmatch("-ab-", -1))
+	fmt.Printf("%q\n", re.FindAllStringSubmatch("-axxb-", -1))
+	fmt.Printf("%q\n", re.FindAllStringSubmatch("-ab-axb-", -1))
+	fmt.Printf("%q\n", re.FindAllStringSubmatch("-axxb-ab-", -1))
+	// Output:
+	// [["ab" ""]]
+	// [["axxb" "xx"]]
+	// [["ab" ""] ["axb" "x"]]
+	// [["axxb" "xx"] ["ab" ""]]
+}
+
+func ExampleRegexp_FindAllStringSubmatchIndex() {
+	re := regexp.MustCompile("a(x*)b")
+	// Indices:
+	//    01234567   012345678
+	//    -ab-axb-   -axxb-ab-
+	fmt.Println(re.FindAllStringSubmatchIndex("-ab-", -1))
+	fmt.Println(re.FindAllStringSubmatchIndex("-axxb-", -1))
+	fmt.Println(re.FindAllStringSubmatchIndex("-ab-axb-", -1))
+	fmt.Println(re.FindAllStringSubmatchIndex("-axxb-ab-", -1))
+	fmt.Println(re.FindAllStringSubmatchIndex("-foo-", -1))
+	// Output:
+	// [[1 3 2 2]]
+	// [[1 5 2 4]]
+	// [[1 3 2 2] [4 7 5 6]]
+	// [[1 5 2 4] [6 8 7 7]]
+	// []
+}
+
+func ExampleRegexp_ReplaceAllLiteralString() {
+	re := regexp.MustCompile("a(x*)b")
+	fmt.Println(re.ReplaceAllLiteralString("-ab-axxb-", "T"))
+	fmt.Println(re.ReplaceAllLiteralString("-ab-axxb-", "$1"))
+	fmt.Println(re.ReplaceAllLiteralString("-ab-axxb-", "${1}"))
+	// Output:
+	// -T-T-
+	// -$1-$1-
+	// -${1}-${1}-
+}
+
+func ExampleRegexp_ReplaceAllString() {
+	re := regexp.MustCompile("a(x*)b")
+	fmt.Println(re.ReplaceAllString("-ab-axxb-", "T"))
+	fmt.Println(re.ReplaceAllString("-ab-axxb-", "$1"))
+	fmt.Println(re.ReplaceAllString("-ab-axxb-", "$1W"))
+	fmt.Println(re.ReplaceAllString("-ab-axxb-", "${1}W"))
+	// Output:
+	// -T-T-
+	// --xx-
+	// ---
+	// -W-xxW-
+}
+
+func ExampleRegexp_SubexpNames() {
+	re := regexp.MustCompile("(?P<first>[a-zA-Z]+) (?P<last>[a-zA-Z]+)")
+	fmt.Println(re.MatchString("Alan Turing"))
+	fmt.Printf("%q\n", re.SubexpNames())
+	reversed := fmt.Sprintf("${%s} ${%s}", re.SubexpNames()[2], re.SubexpNames()[1])
+	fmt.Println(reversed)
+	fmt.Println(re.ReplaceAllString("Alan Turing", reversed))
+	// Output:
+	// true
+	// ["" "first" "last"]
+	// ${last} ${first}
+	// Turing Alan
+}