From: ludo@gnu.org (Ludovic Courtès)
To: Chris Marusich <cmmarusich@gmail.com>
Cc: guix-devel@gnu.org
Subject: Re: isc-bind service draft
Date: Thu, 16 Nov 2017 17:18:00 +0100 [thread overview]
Message-ID: <87fu9eci4n.fsf@gnu.org> (raw)
In-Reply-To: <87tvxuewmq.fsf@gmail.com> (Chris Marusich's message of "Wed, 15 Nov 2017 19:21:49 -0800")
Chris Marusich <cmmarusich@gmail.com> skribis:
> Chris Marusich <cmmarusich@gmail.com> writes:
>
>>>
>>> (define (emit-bind-options-config options)
>>> (match options
>>> (($ <bind-options-configuration> user _ run-directory pid-file
>>> listen-v4 listen-v6 listen-port
>>> allow-recursion? allow-transfer?
>>> allow-update?
>>> version hostname server-id)
>>
>> Some of these slots (e.g., listen-v4) appear to be un-used. Instead of
>> listing positional slots by name, maybe it would be better to bind the
>> entire <bind-options-configuration> to a variable, and then use the
>> accessor procedures (e.g., bind-options-configuration-listen-v4) to get
>> just the attributes you need. This has the benefit of being more
>> resilient to refactorings which change the order of fields in the
>> record, also. I realize that a lot of the code in Guix relies on
>> positional matching of slots like this, so I don't mind if you keep it
>> as-is, but consider my suggestion as food for thought.
>
> FYI, I just learned that there is a way to do this with pattern matching
> in Guile. You can write something like the following:
>
> (match options
> ((? bind-options-configuration? (= bind-options-configuration-listen-v4 listen-v4))
> ;; Do something with listen-v4
> (foo listen-v4)))
>
> As far as I know, this is the same as writing something like:
>
> (match options
> ((? bind-options-configuration? opts)
> (let ((listen-v4 (bind-options-configuration-listen-v4 opts)))
> ;; Do something with listen-v4
> (foo listen-v4))))
In this particular case I would argue that the second version is more
readable.
Ludo’.
next prev parent reply other threads:[~2017-11-16 16:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-09 20:11 isc-bind service draft Oleg Pykhalov
2017-11-15 4:48 ` Chris Marusich
2017-11-16 3:21 ` Chris Marusich
2017-11-16 16:18 ` Ludovic Courtès [this message]
2017-11-24 8:31 ` Oleg Pykhalov
2017-11-30 17:03 ` Ludovic Courtès
2017-11-16 16:19 ` Ludovic Courtès
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