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| From | James Kuyper <jameskuyper@verizon.net> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Untyped Variables |
| Date | 2015-08-08 20:34 -0400 |
| Organization | Self |
| Message-ID | <55C69FFA.7050309@verizon.net> (permalink) |
| References | <83a58dd3-53a6-422a-8502-4fef870baf70@googlegroups.com> <55C61BBF.8090302@verizon.net> <ln37ztfte6.fsf@kst-u.example.com> <8eb33dc8-5c47-4b7b-a20e-584166a50d58@googlegroups.com> |
On 08/08/2015 07:06 PM, David Kleinecke wrote:
...
> I haven't been thinking of constraints as part of syntax. ...
It would be more accurate to say that some constraints constrain the
syntax. For example (6.4.3p1):
> 1 universal-character-name:
> \u hex-quad
> \U hex-quad hex-quad
> hex-quad:
> hexadecimal-digit hexadecimal-digit
> hexadecimal-digit hexadecimal-digit
>
> Constraints
> 2 A universal character name shall not specify a character whose short identifier is less than
> 00A0 other than 0024 ($), 0040 (@), or 0060 (‘), nor one in the range D800 through
> DFFF inclusive.73)
In general, the constrained syntax could alternatively have been
described using only syntax rules. If a constraint was used, it's
generally because expressing the same idea with syntax rules would have
made it much more complex. For example:
universal-character-name:
\u ucn-hex-quad
\U hex-quad hex-quad
hex-quad:
hexadecimal-digit hexadecimal-digit
hexadecimal-digit hexadecimal-digit
ucn-hex-quad:
0 0 2 4
0 0 4 0
0 0 6 0
0 0 a-f hexadecimal-digit
0 one-f hexadecimal-digit hexadecimal-digit
one-c-e-f hexadecimal-digit hexadecimal-digit hexadecimal-digit
D zero-six hexadecimal-digit hexadecimal-digit
D 7 zero-eight hexadecimal-digit
D 7 9 digit
a-f: One of
A B C D E F
one-f: One of
1 2 3 4 5 6 7 8 9 0 A B C D E F
one-c-e-f: One of
1 2 3 4 5 6 7 8 9 A B C E F
zero-six: One of
0 1 2 3 4 5 6
zero-eight: One of
0 1 2 3 4 5 6 7 8
Which is easier to understand - the constrained syntax rules, or the
alternative expressed purely in the form of syntax rules?
Note: if there's any error in my syntax rules for ucn-hex-quad, I won't
be surprised. That merely emphasizes the advantages of using a
constraint rather syntax rules for this kind of thing.
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Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-07 18:19 -0700
Re: Untyped Variables Lőrinczy Zsigmond <nospam@for.me> - 2015-08-08 06:53 +0200
Re: Untyped Variables James Kuyper <jameskuyper@verizon.net> - 2015-08-08 11:09 -0400
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-08 12:09 -0700
Re: Untyped Variables James Kuyper <jameskuyper@verizon.net> - 2015-08-08 14:24 -0400
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-08 12:54 -0700
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-08 16:06 -0700
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-08 17:29 -0700
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-09 17:52 -0700
Re: Untyped Variables Ian Collins <ian-news@hotmail.com> - 2015-08-10 12:57 +1200
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-10 08:41 -0700
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-10 17:06 -0700
Re: Untyped Variables Richard Damon <Richard@Damon-Family.org> - 2015-08-08 19:44 -0400
Re: Untyped Variables James Kuyper <jameskuyper@verizon.net> - 2015-08-08 20:34 -0400
Re: Untyped Variables glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-09 02:03 +0000
Re: Untyped Variables Richard Damon <Richard@Damon-Family.org> - 2015-08-08 22:52 -0400
Re: Untyped Variables glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-09 04:57 +0000
Re: Untyped Variables Joe Pfeiffer <pfeiffer@cs.nmsu.edu> - 2015-08-09 09:58 -0600
Re: Untyped Variables Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-08-10 03:54 -0700
Re: Untyped Variables Richard Damon <Richard@Damon-Family.org> - 2015-08-09 16:59 -0400
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-09 18:02 -0700
Re: Untyped Variables James Kuyper <jameskuyper@verizon.net> - 2015-08-10 11:01 -0400
Re: Untyped Variables James Kuyper <jameskuyper@verizon.net> - 2015-08-10 13:20 -0400
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-10 16:54 -0700
Re: Untyped Variables James Kuyper <jameskuyper@verizon.net> - 2015-08-11 00:20 -0400
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-10 08:11 -0700
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-10 17:15 -0700
Re: Untyped Variables James Kuyper <jameskuyper@verizon.net> - 2015-08-11 00:30 -0400
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-11 16:50 -0700
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-11 17:24 -0700
Re: Untyped Variables Richard Heathfield <rjh@cpax.org.uk> - 2015-08-12 01:37 +0100
Re: Untyped Variables glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-12 04:46 +0000
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-12 18:12 -0700
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-13 12:08 -0700
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-13 16:25 -0700
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-14 10:36 -0700
Re: Untyped Variables Bartc <bc@freeuk.com> - 2015-08-14 19:13 +0100
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-11 07:58 -0700
Re: Untyped Variables richard@cogsci.ed.ac.uk (Richard Tobin) - 2015-08-10 13:53 +0000
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-10 08:29 -0700
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-10 17:01 -0700
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-10 17:42 -0700
Re: Untyped Variables glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-08-11 02:56 +0000
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-10 16:50 -0700
Re: Untyped Variables Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-08-11 01:39 +0100
Re: Untyped Variables Keith Thompson <kst-u@mib.org> - 2015-08-10 19:03 -0700
Re: Untyped Variables Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-08-11 11:21 +0100
Re: Untyped Variables David Kleinecke <dkleinecke@gmail.com> - 2015-08-11 16:37 -0700
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