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

[Marcin Borkowski]

On 2021-05-19, at 18:39, Skip Montanaro <skip.montanaro@gmail.com> wrote:

>> > Yes, use character sets, e.g. [+] and [-].
>
>> Plus "+" is special. Minus "-" is not.
> ...
>> Or escape with backslash. Note that due to string syntax you need
>> two of them.
>
> Yes, correct you are, Tomas. I long ago got used to putting most
> punctuation in character sets regardless of its specialness, if for no
> other reason than to help them stand out when rereading the code
> later. I also find backslashes ugly (especially within Lisp strings
> where there is no such thing as a "raw" string such as in Python, so
> you wind up doubling them). Also, by reflexively putting punctuation
> in character sets I rarely have to remember which are special, or in
> what contexts. For example, "$" is special at the end of a regular
> expression, but not elsewhere. Similarly, "^" is special only at the
> start. The various special cases just make it kind of tedious and easy
> to get wrong. By placing punctuation in character sets you declare to
> the reader, "This is not special, no matter what you might think."
> Well, except for hyphens inside character sets. :) Still, that reduces

And except the caret right after the `['.

> the special cases from N to 1.

So, N to 2.  (Still a win, though.)

Best,

-- 
Marcin Borkowski
http://mbork.pl