elisp: Generic Commands
20.2.4 Select among Command Alternatives
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The macro ‘define-alternatives’ can be used to define “generic
commands”. These are interactive functions whose implementation can be
selected from several alternatives, as a matter of user preference.
-- Macro: define-alternatives command &rest customizations
Define the new command COMMAND, a symbol.
When a user runs ‘M-x COMMAND <RET>’ for the first time, Emacs
prompts for which real form of the command to use, and records the
selection by way of a custom variable. Using a prefix argument
repeats this process of choosing an alternative.
The variable ‘COMMAND-alternatives’ should contain an alist with
alternative implementations of COMMAND. Until this variable is
set, ‘define-alternatives’ has no effect.
If CUSTOMIZATIONS is non-‘nil’, it should consist of alternating
‘defcustom’ keywords (typically ‘:group’ and ‘:version’) and values
to add to the declaration of ‘COMMAND-alternatives’.
Info Catalog
elisp: Interactive Examples
elisp: Defining Commands