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bug#19371: 25.0.50; doc of functions and macros defined in macroexp.el
From: |
Michael Heerdegen |
Subject: |
bug#19371: 25.0.50; doc of functions and macros defined in macroexp.el |
Date: |
Sat, 03 Aug 2019 00:33:14 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
Lars Ingebrigtsen <larsi@gnus.org> writes:
> (defun macroexp-progn (exps)
> - "Return an expression equivalent to \\=`(progn ,@EXPS)."
> + "Return EXPS with `progn' prepended.
> +If EXPS is a single expression, `progn' is not prepended."
> (if (cdr exps) `(progn ,@exps) (car exps)))
That's described a bit confusingly: AFAIU EXPS should always be a list
of expressions, and when it's _a_list_ of only one expression, `progn'
is not prepended and the expression is returned (and not EXPS as your
text suggests). BTW, compared to that description I find the original
version much better (simpler).
> > 2. And then there is `macroexp-let2*', whose doc string says only to
> > bind each binding (bind a binding?!) "as `macrolet2' does". That
> > means nothing. Presumably, based on the `*' in the name, the behavior
> > is similar to that of `let*'. If so, you can use the doc of `let*
> > as inspiration.
>
> Uhm... I have no idea what it does:
>
> (defmacro macroexp-let2* (test bindings &rest body)
> "Bind each binding in BINDINGS as `macroexp-let2' does."
> (declare (indent 2) (debug (sexp (&rest (sexp form)) body)))
> (pcase-exhaustive bindings
> ('nil (macroexp-progn body))
> (`((,var ,exp) . ,tl)
> `(macroexp-let2 ,test ,var ,exp
> (macroexp-let2* ,test ,tl ,@body)))))
You understand what macroexp-let2 does? It supports one binding (a var
plus an expression, specified as separate arguments). macroexp-let2*
supports a list of such pairs specified as BINDINGS, similar to let*.
The naming scheme `macroexp-let2' vs. `macroexp-let2*' is not ideal:
first, because `macroexp-let2' doesn't support multiple bindings like
`let', and secondly because, if I look at the use cases in the sources,
most of them just want to establish multiple bindings, but parallel
binding would suffice, so they actually want to non-stared version of
macroexp-let2*, which is not macroexp-let2 - AFAICT it doesn't exist.
Michael.