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Re: humble proposal: New special form progn-1
From: |
Clément Pit--Claudel |
Subject: |
Re: humble proposal: New special form progn-1 |
Date: |
Wed, 27 Jul 2016 10:08:32 -0400 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0 |
On 2016-07-27 08:16, Tino Calancha wrote:
> Dear all,
>
> i got this idea few days ago (see the patch at the end).
>
> Even though I envision that no one here will like this proposal,
> for me it's instructive to learn from your answers why this is
> not a good idea.
:) I don't have anything strongly against it myself. Any reason to not make it
a lisp macro though?
> My (weak) motivation for introduce this is:
>
> * Compact (and familiar) syntaxis.
> * Same reasons to exists as prog2 has (excluding historical reasons).
> * Other way to acomplish one usual task.
> * Allow lower indentation level (see below):
Sounds good. One worry that I have with the name is that I read it as
(progn)-(1), not prog(n-1).
But in any case, maybe it would be best to make it a lisp macro first?
> ...
> (prog2
> (progn
> (form1)
> (form2)
> (form3)
> .
> .
> .
> (formN-2))
> (prog1
> (formN-1)
> (formN)))
Wouldn't
(progn
(form1)
...
(formN-2)
(prog1
(formN-1)
(formN)))
work?
Cheers,
Clément.
> ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
>> From c9b38c42b253ca004c3aef4dd9dde274aa717d91 Mon Sep 17 00:00:00 2001
> From: Tino Calancha <address@hidden>
> Date: Wed, 27 Jul 2016 20:40:25 +0900
> Subject: [PATCH] New special form progn-1
>
> * src/eval.c (progn-1): Eval sequentially N forms and
> return the value of the form N-1.
> ---
> src/eval.c | 18 ++++++++++++++++++
> 1 file changed, 18 insertions(+)
>
> diff --git a/src/eval.c b/src/eval.c
> index 33b82f7..5eb0cfd 100644
> --- a/src/eval.c
> +++ b/src/eval.c
> @@ -431,6 +431,23 @@ usage: (progn BODY...) */)
> return val;
> }
>
> +DEFUN ("progn-1", Fprogn_1, Sprogn_1, 2, UNEVALLED, 0,
> + doc: /* Eval N forms sequentially; return value from form N-1.
> +usage: (progn-1 FORM_1 FORM_2...FORM_N-1 FORM_N) */)
> + (Lisp_Object body)
> +{
> + Lisp_Object val = Qnil;
> +
> + while (CONSP (XCDR (body)))
> + {
> + val = eval_sub (XCAR (body));
> + body = XCDR (body);
> + }
> + eval_sub (XCAR (body));
> +
> + return val;
> +}
> +
> /* Evaluate BODY sequentially, discarding its value. Suitable for
> record_unwind_protect. */
>
> @@ -3906,6 +3923,7 @@ alist of active lexical bindings. */);
> defsubr (&Sif);
> defsubr (&Scond);
> defsubr (&Sprogn);
> + defsubr (&Sprogn_1);
> defsubr (&Sprog1);
> defsubr (&Sprog2);
> defsubr (&Ssetq);
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