Re: A function to take the regexp-matched subsring directly

[daanturo]

> I suspect it'd be more efficient to iterate directly on the `match-data` 
> rather
> than on an integer (which suffers from an O(N²) complexity).

Got it. By using `substring` directly, it looks like this:

```emacs-lisp
(when (string-match regexp string)
    (let ((matched-data (match-data))
          matches beg end)
      (while matched-data
        (setq beg (pop matched-data))
        (setq end (pop matched-data))
        (push (and beg end
                   (substring string beg end))
              matches))
      (nreverse matches)))
```

> `save-match-data` is costly and extremely rarely needed.

I committed a change that now makes inhibit-modify optional (though `(declare
(pure t) (side-effect-free t))` is lost in the process).


Although I think intuitively, when running those kind of functions, we naturally
expect them not to cause any side-effects from a high-level perspective so
`save-match-data` should be the default.

-- 
Daanturo.

regexp-match.patch
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