From: "Linus Björnstam" <linus.internet@fastmail.se>
To: "Jean Abou Samra" <jean@abou-samra.fr>, guile-user@gnu.org
Subject: Re: Macro to prepend element to list
Date: Sat, 20 Mar 2021 17:04:56 +0100 [thread overview]
Message-ID: <7fbe592f-2816-480d-86ca-3876277d2461@www.fastmail.com> (raw)
In-Reply-To: <7e1286e7-3135-7747-9e25-395ffab3362e@abou-samra.fr>
Well, mutating like that is not very common, except for maybe with alists.
In which situations are you mutating the list like that? Usually you would build a reverse list using a recursive function and an accumulator, which can be done without set! (which has a boxing overhead).
--
Linus Björnstam
On Sat, 20 Mar 2021, at 15:24, Jean Abou Samra wrote:
> Hello,
>
> I find myself frequently using the following macro:
>
> (define-macro (prepend! thing lst)
> `(set! ,lst (cons ,thing ,lst)))
>
> Have I missed a module somewhere that does this kind of things?
> At least, I couldn't find anything in SRFIs. It may also be the
> case that this is too specific to certain non-functional usages
> (LilyPond in my case).
>
> Thanks in advance,
> Jean Abou Samra
>
>
>
next prev parent reply other threads:[~2021-03-20 16:04 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-20 14:24 Macro to prepend element to list Jean Abou Samra
2021-03-20 16:04 ` Linus Björnstam [this message]
2021-03-20 17:05 ` Jean Abou Samra
2021-03-20 18:10 ` Linus Björnstam
2021-03-20 20:16 ` Jean Abou Samra
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