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New conditional compilation macro static-if.

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* etc/NEWS: Record the new macro.

* lisp/subr.el (static-if): New macro.
This commit is contained in:
Alan Mackenzie 2023-09-03 12:54:47 +00:00
parent 6278e15f62
commit 97652d0e7a
2 changed files with 22 additions and 1 deletions
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8
etc/NEWS
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@ -55,7 +55,7 @@ the signature) the automatically inferred function type as well.
---
** New user option 'describe-bindings-outline-rules'.
This user option controls outline visibility in the output buffer of
'describe-bindings' when 'describe-bindings-outline' in non-nil.
'describe-bindings' when 'describe-bindings-outline' is non-nil.
** X selection requests are now handled much faster and asynchronously.
This means it should be less necessary to disable the likes of
@ -861,6 +861,12 @@ Use 'define-minor-mode' and 'define-globalized-minor-mode' instead.
See the "(elisp) Porting Old Advice" node for help converting them
to use 'advice-add' or 'define-advice' instead.
+++
** New macro 'static-if' for conditional compilation of code.
This macro hides a form from the compiler based on a compile-time
condition. This is handy for avoiding byte-compilation warnings about
code that will never actually run under some conditions.
+++
** Desktop notifications are now supported on the Haiku operating system.
The new function 'haiku-notifications-notify' provides a subset of the

15
lisp/subr.el
View file

@ -277,6 +277,21 @@ change the list."
(macroexp-let2 macroexp-copyable-p x getter
`(prog1 ,x ,(funcall setter `(cdr ,x))))))))
;; Note: `static-if' can be copied into a package to enable it to be
;; used in Emacsen older than Emacs 30.1. If the package is used in
;; very old Emacsen or XEmacs (in which `eval' takes exactly one
;; argument) the copy will need amending.
(defmacro static-if (condition then-form &rest else-forms)
"A conditional compilation macro.
Evaluate CONDITION at macro-expansion time. If it is non-nil,
expand the macro to THEN-FORM. Otherwise expand it to ELSE-FORMS
enclosed in a `progn' form. ELSE-FORMS may be empty."
(declare (indent 2)
(debug (sexp sexp &rest sexp)))
(if (eval condition lexical-binding)
then-form
(cons 'progn else-forms)))
(defmacro when (cond &rest body)
"If COND yields non-nil, do BODY, else return nil.
When COND yields non-nil, eval BODY forms sequentially and return