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Document and-let* vs. when-let* usage convention

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* lisp/subr.el (and-let*): Document and/and-let*
vs. when/when-let* usage convention (some discussion in
bug#73853).
(when-let*): Add cross-reference to and-let*.
This commit is contained in:
Sean Whitton 2024-10-23 09:07:06 +08:00
parent b7a375f5c4
commit 09e05f7ee4
1 changed files with 10 additions and 2 deletions
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@ -2640,14 +2640,22 @@ This is like `if-let' but doesn't handle a VARLIST of the form
(defmacro when-let* (varlist &rest body)
"Bind variables according to VARLIST and conditionally evaluate BODY.
This is like `when-let' but doesn't handle a VARLIST of the form
\(SYMBOL SOMETHING) specially."
\(SYMBOL SOMETHING) specially.
See also `and-let*'."
(declare (indent 1) (debug if-let*))
(list 'if-let* varlist (macroexp-progn body)))
(defmacro and-let* (varlist &rest body)
"Bind variables according to VARLIST and conditionally evaluate BODY.
Like `when-let*', except if BODY is empty and all the bindings
are non-nil, then the result is the value of the last binding."
are non-nil, then the result is the value of the last binding.
Some Lisp programmers follow the convention that `and' and `and-let*'
are for forms evaluated for return value, and `when' and `when-let*' are
for forms evaluated for side-effect with returned values ignored."
;; Document this convention here because it partially explains why we
;; have both `when-let*' and `and-let*'.
(declare (indent 1) (debug if-let*))
(let (res)
(if varlist