Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #18471

Re: A very simple parser with scanf & C

Show all headers | View raw

Tim Rentsch wrote:
> 
> pete <pfiland@mindspring.com> writes:
> 
> > Tim Rentsch wrote:
> >>
> >> pete <pfiland@mindspring.com> writes:
> >>
> >> > Tim Rentsch wrote:
> >> >
> >> >> [snip]
> >
> > If you're going to say for {char c;}
> >
> >>>     isalpha( * (unsigned char*) &c )
> >>>
> >>> rather than
> >>>
> >>>     isalpha(   (unsigned char )  c )
> >
> > then I think we should consider a case where
> >     ( * (unsigned char*) &c )
> > is different from
> >     (   (unsigned char )  c )
> > and the only case I can think of,
> > is where (c) is signed, negative and not twos complement.
> 
> Right (ignoring padding bits in char, which no sane
> implementation has), although actually there is one other
> case, namely a two's complement trap representation.  Not
> very likely perhaps but it is allowed, so for the sake of
> completeness I think it should be mentioned.  (And now it
> has been...)

Considering that file operations are at the root of this thread:

If char is signed, and char c is assigned a value of (-1), as in
    char c;
    c = -1;

and if (c) is written to a file using fputc,
then the value written into the file will be ((unsigned char)-1).

If that same byte is read back from the same file using fgetc,
then the value returned by fgetc will be
((int)(unsigned char)-1)
which is equal to ((unsigned char)c)
regardless of the representation of negative integers.

The return value of fgetc will be unequal to 
( * (unsigned char*) &c )
when negative integers are either sign and magnitude
or one's complement.

-- 
pete

Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

A very simple parser with scanf & C pozz <pozzugno@gmail.com> - 2011-09-23 07:03 -0700
  Re: A very simple parser with scanf & C Nobody <nobody@nowhere.com> - 2011-09-23 18:28 +0100
  Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-23 18:29 +0100
    Re: A very simple parser with scanf & C pozz <pozzugno@gmail.com> - 2011-09-23 23:16 +0200
      Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-24 00:09 +0100
        Re: A very simple parser with scanf & C pozz <pozzugno@gmail.com> - 2011-09-24 09:32 +0200
  Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-23 21:24 +0100
    Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-23 22:00 +0100
      Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-24 00:04 +0100
        Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-24 00:34 +0100
          Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-24 01:00 +0100
            Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-24 02:42 +0100
              Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-24 12:13 +0100
                Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-24 12:25 +0100
                Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-24 15:05 +0100
                Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-24 14:45 +0100
                Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-24 17:45 +0100
                Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-24 22:21 +0100
                Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-25 00:52 +0100
                Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-25 01:54 +0100
                Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-25 02:51 +0100
                Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-25 12:22 +0100
                Re: A very simple parser with scanf & C Gene <gene.ressler@gmail.com> - 2011-09-25 01:35 -0700
                Re: A very simple parser with scanf & C pete <pfiland@mindspring.com> - 2011-09-25 08:41 -0400
                Re: A very simple parser with scanf & C Gene <gene.ressler@gmail.com> - 2011-09-25 11:23 -0700
                Re: A very simple parser with scanf & C Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-09-25 19:41 +0300
                Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-25 19:45 +0100
                Re: A very simple parser with scanf & C Keith Thompson <kst-u@mib.org> - 2011-09-25 12:10 -0700
                Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-25 20:43 +0100
                Re: A very simple parser with scanf & C James Kuyper <jameskuyper@verizon.net> - 2011-09-25 15:55 -0400
                Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-26 11:07 +0100
                Re: A very simple parser with scanf & C Richard Damon <news.x.richarddamon@xoxy.net> - 2011-09-26 11:40 -0400
                Re: A very simple parser with scanf & C Keith Thompson <kst-u@mib.org> - 2011-09-26 12:22 -0700
                Re: A very simple parser with scanf & C pacman@kosh.dhis.org (Alan Curry) - 2011-09-26 21:19 +0000
                Re: A very simple parser with scanf & C Keith Thompson <kst-u@mib.org> - 2011-09-26 16:11 -0700
                Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-26 23:26 +0100
                Re: A very simple parser with scanf & C Keith Thompson <kst-u@mib.org> - 2011-09-26 12:18 -0700
                Re: A very simple parser with scanf & C Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-09-27 02:27 +0300
                Re: A very simple parser with scanf & C Keith Thompson <kst-u@mib.org> - 2011-09-27 10:06 -0700
                Re: A very simple parser with scanf & C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2011-09-27 21:10 +0100
                Re: A very simple parser with scanf & C Seebs <usenet-nospam@seebs.net> - 2011-09-26 22:59 +0000
                Re: A very simple parser with scanf & C Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-09-30 05:18 -0700
                Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-30 17:06 +0100
                Re: A very simple parser with scanf & C Richard Damon <news.x.richarddamon@xoxy.net> - 2011-09-25 18:05 -0400
                Re: A very simple parser with scanf & C Keith Thompson <kst-u@mib.org> - 2011-09-25 15:30 -0700
                Re: A very simple parser with scanf & C Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-24 14:01 -0800
                Re: A very simple parser with scanf & C pete <pfiland@mindspring.com> - 2012-01-25 11:05 -0500
                Re: A very simple parser with scanf & C Tim Rentsch <txr@alumni.caltech.edu> - 2012-01-31 16:01 -0800
                Re: A very simple parser with scanf & C pete <pfiland@mindspring.com> - 2012-01-31 23:47 -0500
                Re: A very simple parser with scanf & C Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-08 09:21 -0800
                Re: A very simple parser with scanf & C pete <pfiland@mindspring.com> - 2012-03-10 15:18 -0500
                Re: A very simple parser with scanf & C Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-13 15:49 -0700
                Re: A very simple parser with scanf & C pete <pfiland@mindspring.com> - 2012-03-14 18:56 -0500
                Re: A very simple parser with scanf & C Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-15 17:37 -0700
                Re: A very simple parser with scanf & C pete <pfiland@mindspring.com> - 2012-03-17 00:24 -0500
                Re: A very simple parser with scanf & C Tim Rentsch <txr@alumni.caltech.edu> - 2012-03-21 05:21 -0700
    Re: A very simple parser with scanf & C pozz <pozzugno@gmail.com> - 2011-09-23 23:23 +0200
      Re: A very simple parser with scanf & C "BartC" <bc@freeuk.com> - 2011-09-23 23:53 +0100
  Re: A very simple parser with scanf & C Rui Maciel <rui.maciel@gmail.com> - 2011-09-25 14:07 +0100

csiph-web