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bug#52290: 28.0.90; Undocumented generalized variables
From: |
Michael Heerdegen |
Subject: |
bug#52290: 28.0.90; Undocumented generalized variables |
Date: |
Sun, 05 Dec 2021 17:17:12 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) |
Lars Ingebrigtsen <larsi@gnus.org> writes:
> [...] I.e., all the generalised variables that are used for side
> effect (as opposed to mutating an explicit object) are liable to cause
> confusion.
I would want to limit this to the kind of side effect: is it undoubtedly
clear what it is, is there a "canonical" side effect? This is the case
e.g. for `buffer-modified-p' to a high degree, but not for
e.g. `point-max': there are several ways to achieve that `point-max'
will return a certain value - killing a certain amount of text, for
example. Or narrowing. Narrowing was not the thing that came to my
mind first. A setter for it might cause confusion because the semantics
are not clear, in contrast to `buffer-modified-p', I think, where it is
quite clear.
I mean, Emacs is an editor, so we have more aspects of state than
variable bindings. Setting variables can also have other side effects
than simply changing the variable's binding. Per se I don't see a
problem in considering more kinds of state (more than variables) as
places. OTOH, `point-max' for example is not really a self-contained
part of state, it's a value of a computation, a derived value.
The classification result can be a bit subjective and depend on the
viewing point, of course.
Michael.
bug#52290: 28.0.90; Undocumented generalized variables, Phil Sainty, 2021/12/04
bug#52290: 28.0.90; Undocumented generalized variables, Richard Stallman, 2021/12/05