Re: Isearch interaction model

[Juri Linkov]

>>> The isearch mode should be attached to the history item. C-M-s M-p and
>>> C-s
>>> M-p should have the same effect: the "mode" is only a default for a new
>>> search. If the last search was a regex search, it'll put in you regex
>>> search mode.
>>
>> But what about keeping current behavior where C-M-s M-p pulls only
>> regexps from the regexp history.  Should we break backward compatibility
>> in how it used to work?
>
> I think that behavior is an artifact of the current implementation, not
> something desirable.

String and regexp searches are fundamentally different in nature.
Regexps are useless in string-based modes, whereas strings in isearch
are interpreted by different rules according to mode: word/case-fold/...
e.g. it makes sense to switch from case-fold mode to word mode, but
not from regexp mode to literal mode.

But it you want to share string and regexp histories, it's easy to implement
by another layer of indirection like for query-replace history variables:

(defcustom query-replace-from-history-variable 'query-replace-history
(defcustom query-replace-to-history-variable 'query-replace-history