Date: Fri, 05 Dec 2008 13:45:28 +0200 From: Andriy Gapon <avg@icyb.net.ua> To: Garrett Cooper <yanefbsd@gmail.com> Cc: Maksim Yevmenkin <maksim.yevmenkin@gmail.com>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: RFC: small syscons and kbd patch Message-ID: <49391458.8060708@icyb.net.ua> In-Reply-To: <7d6fde3d0812050050l57684eebkf14f252d78b68ec0@mail.gmail.com> References: <bb4a86c70812021701i621fdcfjb6a58a7f5cf781d5@mail.gmail.com> <7d6fde3d0812040324y3bf0901cy1f4a6d961362c314@mail.gmail.com> <bb4a86c70812040724w43ddec15yab72920d80d879d3@mail.gmail.com> <20081205072229.GE18652@hoeg.nl> <7d6fde3d0812050034y43a70ce8i49fbba92f9c8943b@mail.gmail.com> <7d6fde3d0812050035u6e3ea930o9e093830a8608444@mail.gmail.com> <20081205084441.GA29312@owl.midgard.homeip.net> <7d6fde3d0812050050l57684eebkf14f252d78b68ec0@mail.gmail.com>
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on 05/12/2008 10:50 Garrett Cooper said the following:
> On Fri, Dec 5, 2008 at 12:44 AM, Erik Trulsson <ertr1013@student.uu.se> wrote:
>> On Fri, Dec 05, 2008 at 12:35:31AM -0800, Garrett Cooper wrote:
>>> On Thu, Dec 4, 2008 at 11:22 PM, Ed Schouten <ed@80386.nl> wrote:
>>>> * Maksim Yevmenkin <maksim.yevmenkin@gmail.com> wrote:
>>>>> the idea was to ensure that kbd->kb_locked variable only takes values
>>>>> 0 (zero) and 1 (one).
>>>> I often use constructs like these to do that:
>>>>
>>>> foo = bar ? 1 : 0;
>>>>
>>>> Maybe !!bar is a lot shorter to write, I think the line above is a lot
>>>> easier to read.
>>> Indeed. I had no idea (and I would assume that many people wouldn't in
>>> my similar level of systems programming) what in the work you were
>>> trying to do above with that line. The one-line conditional is
>>> universal in almost all major high-level language dialects I've hit,
>>> minus Python and Tcl.
>>> -Garrett
>> The !!bar construction to map {0, not-0} to {0,1} is fairly common in C
>> programming, and I would certainly expect any experienced C programmer to
>> recognize it.
>
> (I feel like I'm getting off on a bikeshed topic, but...)
>
> 1. What dialect of C was it defined in? Is it still used in the
> standard dialect (honestly, this is the first time I've ever seen it
> before, but then again I am a younger generation user)?
I am not sure what you meant by dialect of C, just in case you meant
something different from others understood here's my personal
observation: you will quite a bit of '!!' in Linux kernel code, you
would see much much fewer of them in our code.
--
Andriy Gapon
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