From: Neil Jerram <neil@ossau.homelinux.net>
To: Christopher Howard <christopher.howard@qlfiles.net>, guile-user@gnu.org
Subject: Re: Signals / Messages / Events / ...?
Date: Wed, 3 Jan 2018 19:53:28 +0000 [thread overview]
Message-ID: <e0b03c54-0283-1162-3ea2-8a646b2faac6@ossau.homelinux.net> (raw)
In-Reply-To: <1514992280.4049.5.camel@qlfiles.net>
On 03/01/18 15:11, Christopher Howard wrote:
> On Wed, 2018-01-03 at 11:53 +0000, Neil Jerram wrote:
>> Well, one Lispy mechanism in that area is hooks. For example, from
>> some
>> of my old code:
>>
>> ;; Changes to modem registration state are indicated by calling this
>> ;; hook with args STATE and PROPERTIES. STATE can be 'none, meaning
>> ;; that there is currently no modem; 'unregistered, meaning that
>> there
>> ;; is a modem but it isn't registered with the network; or
>> ;; 'registered, meaning that the modem is registered with the
>> network.
>> ;; If STATE is 'registered, PROPERTIES is an alist of registration
>> ;; properties; otherwise PROPERTIES is #f.
>> (define registration-hook (make-hook 2))
>>
>> (define (add-registration-hook proc)
>> (add-hook! registration-hook proc))
>>
>> (define (notify-registration state properties)
>> (run-hook registration-hook state properties))
>>
>> Does that serve your purpose at all?
>>
>> Best wishes - Neil
>>
>>
> I think that should work. Only part I'm not sure about is if you can
> have a "one-off" procedure added to a hook... but you could just have
> the procedure call remove-hook! to remove itself...?
>
Yes, I think so, and you could encapsulate that with something like this:
(define (add-hook-once-only! hook proc)
(letrec ((proc-once-only
(lambda args
(remove-hook! hook proc-once-only)
(apply proc args))))
(add-hook! hook proc-once-only)))
Best wishes - Neil
next prev parent reply other threads:[~2018-01-03 19:53 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-03 5:09 Signals / Messages / Events / ...? Christopher Howard
2018-01-03 11:53 ` Neil Jerram
2018-01-03 15:11 ` Christopher Howard
2018-01-03 19:53 ` Neil Jerram [this message]
2018-01-04 1:16 ` Matt Wette
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