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Re: cl-defmethod specializer widget ?
From: |
Stefan Monnier |
Subject: |
Re: cl-defmethod specializer widget ? |
Date: |
Thu, 27 Jan 2022 01:28:46 -0500 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) |
> I wonder why it is not possible to use widget as specializer in cl-defmethod.
Because the current code only works for types that can be inferred
solely from the value of (type-of OBJ), basically.
You can add support for `widget` as a specializer in two ways:
- Redefine widgets to use their own *real* type (i.e. with
`cl-defstruct`) instead of (ab)using symbols and cons cells.
- Add a method to `cl-generic-generalizers` to handle `widget` in an
ad-hoc way.
> Indeed it is not declared in the suitable list but could
> it be added without trouble ;
It would slow down dispatch, but only of those generic functions that
contain methods specializing on `widget`.
> Similarly function is not accepted but it could be comfortable .
Indeed, for the same reason: a value of the form (closure ...) or
(lambda ...) is a valid function, currently, but `type-of` returns
`cons` and not all `cons` are functions, so it would require
an additional method in `cl-generic-generalizers`.
Stefan