Add support backslash reference in Replace()

[vkd]

Test case:

func TestReplaceRef(t *testing.T) {
	re := MustCompile("(123)hello(789)", None)
	res, err := re.Replace("123hello789", "\\1456\\2", -1, -1)
	if err != nil {
		t.Fatal(err)
	}
	if res != "123456789" {
		t.Fatalf("Wrong result: %s", res)
	}
}

Result:

--- FAIL: TestReplaceRef (0.00s)
	regexp_test.go:775: Wrong result: \1456\2

[dlclark]

Which languages regex spec are you wanting this to be modeled after?

There are lots of features related to the $ replace syntax (https://msdn.microsoft.com/en-us/library/ewy2t5e0(v=vs.110).aspx) so the implementation is a bit more involved than just allowing \ or $ to start reference groups in replace strings.

[vkd]

Sorry, I confused and forgot that this package based on .NET regexp engine.

This issue may be closed.