Constructing a dynamic regex

Faki · 03-06-2023, 08:33 PM

I want to use the following variables

Code:

pbseq = "\[\{\("
qbseq = "\]\}\)"

to construct the following dynamic regex pattern

Code:

rl = "^[" pbseq "]|[" qbseq "]$"

What I get is

Code:

warning: escape sequence `\[' treated as plain `['

This could mean that I need some modification to pbseq and qbseq.

The idea is to construct

Code:

rl = "^[\[\{\(]|[\]\}\)]$"

using literal opening [{( and closing ]})

scasey · 03-06-2023, 09:27 PM

Escape the slash?

Code:

pbseq = "\\[\{\("

Faki · 03-07-2023, 06:56 AM

So the first backslash is used to escape the second backslash, which is itself used to escape the "[".

Does this apply also to all opening and closing brackets [ { ( ] } ) ?

pan64 · 03-07-2023, 07:21 AM

Quote:

Originally Posted by Faki

So the first backslash is used to escape the second backslash, which is itself used to escape the "[".

Does this apply also to all opening and closing brackets [ { ( ] } ) ?

you need to understand how quotation works otherwise you will never know how to use those backslashes (if you need one, two or more of them).
Also you need to learn how quotation works to understand when do you need quote and what. It always depend on the actual context and language, there is no general answer.

Faki · 03-07-2023, 07:26 AM

Can get quite complicated as you say, with multiple backslashes. As for the question I am constructing a dynamic regex that matches opening and closing literal brackets.

Code:

pbseq = "\\[\\{\\("  # Match literal opening brackets.
qbseq = "\\]\\}\\)"  # Match literal closing brackets. 
rl = "^[" pbseq "]|[" qbseq "]$"

What quotation workings need I understand, and what should I read exactly ?