Why regular expression doesn't work with bracket?

[vivo]

I have below codes. Why the regular expression doesn't work with {2}? The last 2 lines should be 1b instead. How to make it work? Thanks.

"42" like "[0-9][0-9]"; // i.e. 1b
"42" like "[0-9]{2}"; // i.e. 0b 
"42" like "[0-9]{2,2}"; // i.e. 0b

[gyorokpeter-kx]

The patterns used by like are not actual regular expressions, so they don't support this {n} syntax. I think the naming is unfortunate.

Regular expressions in q | Basics | q and kdb+ documentation - Kdb+ and q documentation (kx.com)

[rocuinneagain · Accepted solution]

kdb+ does not implement full regex.

https://code.kx.com/q/basics/regex/

It supports ? * [] ^

If you want full support you can use the C interface to bring in external libraries 

• https://code.kx.com/q/basics/regex/#regex-libraries 
• https://code.kx.com/developer/libraries/regular-expression-pcre2/ 
• https://github.com/KxSystems/ffi/blob/master/examples/pcre.q