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Re: A very simple parser with scanf & C

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Tim Rentsch wrote:
 
> My understanding is that a cast to (unsigned char) may not
> give exactly the right behavior.  In particular, if we have
> a variable 'char c;' then to call a function like 'isalpha()'
> we need to do
> 
>     isalpha( * (unsigned char*) &c )
> 
> rather than
> 
>     isalpha(   (unsigned char )  c )
> 
> to get exactly the same behavior as happens for getchar(), etc.
> 
> Of course, on most current machines these two methods give
> the same results, but as a matter of correctness the first
> form is the better one.  Right?


I don't think so.
If you were to output the value of (c) using fputc, 
then the return value of the function call would be
 ((int)(unsigned char)c).

Th value of (c) "converted to unsigned char" is ((unsigned char)c).

N869
4.9.7.3 The fputc function
Synopsis
         #include <stdio.h>
         int fputc(int c, FILE *stream);
Description
   The fputc function writes the character specified by c 
   (converted to an unsigned char ) ...


Also, isalpha also has to be able to work with arguments 
which may be constant expressions that don't have addresses.

Given

#define NEG_A   ('A' - 1 - (unsigned char)-1)

then isalpha ((unsigned char)NEG_A) should return nonzero

and putchar((unsigned char)NEG_A) should return ('A')

-- 
pete

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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

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