RE: [External] : Use the characters "+" and "-" in regular expressions

[Drew Adams]

> Is there a way to use the character "+" and "-" in regular expressions?

Ask Emacs!

1. `C-h i' Choose Elisp manual.
2. `i regexp TAB', and complete to
   `regexp, special characters in'
3. Read about `\':

   it quotes the special characters

   Because ‘\’ quotes special characters, ‘\$’ is a
   regular expression that matches only ‘$’, and ‘\[’ is
   a regular expression that matches only ‘[’, and so on.

IOW, `\+' and `\-' match (only) `+' and `-', respectively.

Another way to match special chars literally is to include
them in a character alternative, also described in the same
page of the manual.

`[+]' matches only `+', `[-]' matches only `+' or `-', and
`[-+]' and `[+-]' match either `+' or `-'.

Note too that `-' in a char alternative behaves specially:

   To include a ‘-’, write ‘-’ as the first or last
   character of the character alternative, or as the
   upper bound of a range.  Thus, ‘[]-]’ matches both
   ‘]’ and ‘-’.

In `[-+]' and `[+-]', the `-' is the first or last char in
the alternative.