RegExp Named Groups

[seadoggie01]

Disclaimer: I'm sure there is an easier way to do this without regex, but I like regex and the challenge.

I have a date input in my GUI and I need to validate it and extract the year and month to enter them into another program. It accepts this format: YYYY-MM

This is what I have currently:

$DATE_PATTERN = "(?|([0-9]{4})[-\/\\]([0-9]{2})|([0-9]{2})[-\/\\]([0-9]{4}))"
$Date = "2014/04"
Msgbox($MB_OK, "Result", StringRegExpReplace($Date, $DATE_PATTERN, "\1-\2"))
;~  (Returns "2014-04")

This works, but with 04/2014 it returns 04-2014 instead. This is what I want to work, but named groups don't seem to work like this...

$DATE_PATTERN = "(?|(?<year>[0-9]{4})[-\/\\](?<month>[0-9]{2})|(?<month>[0-9]{2})[-\/\\](?<year>[0-9]{4}))"
$Date = "2014/04"
Msgbox($MB_OK, "Result", StringRegExpReplace($Date, $DATE_PATTERN, "\year-\month"))
;~  (Returns original code -- no match)

I tried my code here: https://regex101.com/r/iJ9tC7/23  and it says that named groups can't be named that way. Is there a way to do this nicely in RegEx? I'm losing hope in it

Edited March 6, 2019 by seadoggie01
Forgot to change replace pattern

[FrancescoDiMuro]

@seadoggie01
This is because backreferencing named capturing groups in substitutions, is not supported in PCRE engine 
 

[jchd]

A simple regexp can't do that this way. Not only patterns (named or not) only live while the regex engine scans the subject. PCRE (at least PCRE1 which is implemented in current AutoIt versions) has no support for substitution. The Replace part is an AutoIt construct which can only recognize $1, $2, $3, ... (or equivalently \1, \2, \3, ...) as a sugar for successive capturing groups.

Due to the way regex works (try to match the pattern by scanning the subject left to right), you can't exchange the role of $1 and $2 depending on their content or order of matching.

Yet there is a simple possibility: give up duplicate pattern numbering!

Local $aDate = ["2014/04", "2014-04", "04-2014", "04\2014", "04/2014", "2014\04"]
Local $DATE_PATTERN = "(\d{4})[-\/\\](\d{2})|(\d{2})[-\/\\](\d{4})"
For $d In $aDate
    ConsoleWrite($d & "  -->  " & StringRegExpReplace($d, $DATE_PATTERN, "$1$4-$2$3") & @LF)
Next

Forcing capture of distinct fix-length subpatterns works, since what isn't matched yields an empty string, which we may concatenate transparently.

[seadoggie01]

@FrancescoDiMuro Oh. Go figure

@jchd  Dang! I remember thinking about something like that! (Probably tried and determined it wasn't possible) That's perfect!!!! Thank you!