I suggest two changes.
First, always use backquotes `` around regular expressions to avoid
misunderstandings should a backslash occur.
Second, in this case if M|m is just a choice and not a subexpression you
need to track, you can make it easier to read by using character classes to
reduce the number of parentheses. It is easier to read therefore. You will
need to adjust the code that uses subexpression matching. I did this by
hand and didn't test it, but it will give you the idea:
`([Mm][Pp])[34])|([Ff][Ll][Aa][Cc])$`
In fact, if you don't need subexpressions there are no parentheses needed,
as the alternation operator groups as you would expect.
`[Mm][Pp][34]|[Ff][Ll][Aa][Cc]$`
However, I suspect at least some of the elements must be parenthesized for
the job at hand.
-rob
On Wed, Feb 15, 2023 at 2:51 AM Howard C. Shaw III <howardcs...@gmail.com>
wrote:
> var ExtRegex =
> regexp.MustCompile("(M|m)(p|P)(3|4))|((F|f)(L|l)(A|a)(C|c))$")
>
> with a
> ./prog.go:10:18:
> regexp.MustCompile("((M|m)(p|P)(3|4))|((F|f)(L|l)(A|a)(C|c))$") (value of
> type *regexp.Regexp) is not constant
>
>
> Actual error I get is "error parsing regexp: unexpected ):
> `(M|m)(p|P)(3|4))|((F|f)(L|l)(A|a)(C|c))$`"
> It is missing a parentheses. This compiles fine:
>
> var ExtRegex =
> regexp.MustCompile("((M|m)(p|P)(3|4))|((F|f)(L|l)(A|a)(C|c))$")
> Note that there are two parentheses after the double-quote.
>
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