Why does save-match-data do what it does?

Why does save-match-data do what it does?

[Marcin Borkowski]

Hi all,

save-match-data works by assigning the current match data to a temporary
variable, doing its stuff and restoring it again.  Why not this?

--8<---------------cut here---------------start------------->8---
(defmacro save-match-data-icmd (&rest body)
  "An alternative definition of `save-match-data'."
  (declare (indent 0) (debug t))
  `(let ((inhibit-changing-match-data t))
     ,@body))
--8<---------------cut here---------------end--------------->8---

(Of course, without the quoting, for the reason mentioned in subr.el.)

TIA,

--
Marcin Borkowski
http://mbork.pl

Re: Why does save-match-data do what it does?

[Robert Pluim]

Marcin Borkowski <mbork@mbork.pl> writes:

> Hi all,
>
> save-match-data works by assigning the current match data to a temporary
> variable, doing its stuff and restoring it again.  Why not this?
>
> (defmacro save-match-data-icmd (&rest body)
>   "An alternative definition of `save-match-data'."
>   (declare (indent 0) (debug t))
>   `(let ((inhibit-changing-match-data t))
>      ,@body))

What if body want to use match data?

Robert

Re: Why does save-match-data do what it does?

[Marcin Borkowski]

On 2018-03-07, at 10:55, Robert Pluim <rpluim@gmail.com> wrote:

> Marcin Borkowski <mbork@mbork.pl> writes:
>
>> Hi all,
>>
>> save-match-data works by assigning the current match data to a temporary
>> variable, doing its stuff and restoring it again.  Why not this?
>>
>> (defmacro save-match-data-icmd (&rest body)
>>   "An alternative definition of `save-match-data'."
>>   (declare (indent 0) (debug t))
>>   `(let ((inhibit-changing-match-data t))
>>      ,@body))
>
> What if body want to use match data?

What is the offical ascii art for a person clapping their forehead with
their palm?

Thanks!

-- 
Marcin Borkowski
http://mbork.pl