Date: Fri, 5 Dec 2008 16:05:21 +0300 From: Eygene Ryabinkin <rea-fbsd@codelabs.ru> 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: <WUFHrI95zEo9/wlGGrRYnWztEtI@qm7gbYKMPO53E/nl%2BD5eD8YyL1A> 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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Garret,
Fri, Dec 05, 2008 at 12:50:38AM -0800, Garrett Cooper wrote:
> 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)?
It is the standard negation operator: !(expr) is equal to (expr =3D=3D 0).
> 2. Is it still taught in schools (I didn't learn it when I was taught
> C)?
Yes. I am personally teaching the people in school and I am explaining
the concept of double negation every two years ;))
> If not in schools, what about the Richie text (it's sort of like
> the defacto C programming standard book of course)?
K&R book is good but it at no means covers all tricks and idioms
of a C language.
> 3. What's the real loss of going to `? :', beyond maybe 3 extra
> keystrokes if it's easier for folks who may not be as experienced to
> read?
No real loss, just easier to type and looks more compact. It is the
matter of a personal taste, I think.
If one knows this idiom, he will recognize it at a glance. If not, one
should think a bit about the logics behind it, but it shouldn't be hard:
almost everyone uses constructs like 'if (!ptr)'. And there is only one
step from there to the double negation.
--=20
Eygene
_ ___ _.--. #
\`.|\..----...-'` `-._.-'_.-'` # Remember that it is hard
/ ' ` , __.--' # to read the on-line manual =20
)/' _/ \ `-_, / # while single-stepping the kernel.
`-'" `"\_ ,_.-;_.-\_ ', fsc/as #
_.-'_./ {_.' ; / # -- FreeBSD Developers handbook=20
{_.-``-' {_/ #
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