Re: Use the characters "+" and "-" in regular expressions

[tomas]

On Wed, May 19, 2021 at 11:17:34AM -0500, Skip Montanaro wrote:
> > Is there a way to use the character "+" and "-" in regular expressions?

Plus "+" is special. Minus "-" is not.

> Yes, use character sets, e.g. [+] and [-]. If more characters are in a set
> along with a hyphen, that hyphen needs to be the first element of the set
> so as not to be interpreted as defining a range of characters. So, the
> character set containing 0, 9 and hyphen is [-09] or [-90], not [0-9],
> which would include all digits between 0 and 9, but not the hyphen.

Or escape with backslash. Note that due to string syntax you need
two of them.

Besides, the '-' isn't a special character in regexps (except whithin
brackets), so your bracket trick is rather counter-productive. Just
use as-is (except in brackets, where it should, as you say, go last,
to distinguish it from a range marker).

  (string-match "-" "Viala-du-Tarn")
  => 5

Cheers
 - t

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