HPCC ECL REGEX lookaround back-to-back values

Question

I am using the REGEX Library as defined here http://userguide.icu-project.org/strings/regexp

That being said I have a specific problem I would like to use regex to correct.

Input := '!Tim !~ Dan~'; 
Output := Tim !~ Dan

REGEXREPLACE('((?<![!])~)' ,Input,' '); //Results in : !Tim !~ Dan
REGEXREPLACE('((?![~])!)|((?<![!])~)',Input,' '); //Results in : Tim ~ Dan

What about this statement is causing the ! following the ~ to be removed?

How do I remove all ! and ~ without removing the combination of !~ in a single Regex command.

BONUS POINTS if you can tell me how to make !~! work in a single command.

Thanks!!

Answer 1

You can use the following regex:

(!~)|[!~]

and replace with $1 backreference. See the regex demo.

Details:

• (!~) - matches and captures into Group 1 a !~ sequence of characters
• | - or
• [!~] - a single ! or ~ character

The $1 backreference re-inserts the value stored in Group 1 back to the resulting string.