From: "Tim Nicholson" <T DOT J DOT Nicholson AT btinternet DOT com>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Please add strrev proposal
Date: Sat, 29 Sep 2001 21:15:04 +0100
Organization: Skyforce avionics Limited
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To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Reply-To: djgpp AT delorie DOT com

I can't claim to fully understand what your last message was trying to tell
me, but, like it or not, the statement:

printf("%s %s",str,strrev(str));

will print the reverse string twice on every version of C you care to try it
on.

BTW

I did not intend to imply that printf() would call anything, I just
attempted to point out that it would have to if it was to behave the way you
seem to think it should!

I recommend that you try coding it for real rather than quote a load of out
of context snippets!

(No offence)

Tim

<Radical NetSurfer> wrote in message
news:02pbrto99332j0s1mnkvhl4sts5828rqiu AT 4ax DOT com...
> At the risk of being redundant:
>
> <begin_being_redundant>
> If your compiler actually outputs both strings as reversed,
> THEN I am very scared your compiler is quite BROKEN.
>
> printf("format specifier1, format_specififer2", var1, func1);
>
> does:
> display __current__ value of   var1 FIRST using format_specifier1,
> __THEN__
> display __output__ of  funct1 using format_specifier2,
>
> { there just is not any other way to say this more clearly }
>
> [[snippity-snip]]
>
> { Print, }
> Left to right, in the order AND STATE ENCOUNTERED!
> { values, values_to_functions }
>
> ....however... __AFTER__ the call to   printf(), __THEN__
> 'str' will contain the result of the function call;
> but
>         __NEVER__
>                                     from  __WITHIN__ the printf   as
> you implied.  Your post is VERY MISLEADING.
> <end_being_redundant>
>
> { and that will be all I will offer to this thread }
>
> On Sat, 29 Sep 2001 14:52:36 +0100, "Tim Nicholson"
> <T DOT J DOT Nicholson AT btinternet DOT com> wrote:
>
> >If you think about it, it could not work any other way. The string only
> >exists in one state or the other. (i.e. forward state or reverse state)
It
> >would therefore not be possible to pass both states to the printf()
function
> >as parameters in the same call. The only way your reasoning could work is
if
> >printf() were to call strref(str) having processed the first %s and, of
> >cource, that is not how any function works.
> >
> >Tim
> ><Radical NetSurfer> wrote in message
> >news:vhpart0gjqnr7u2tf0ih8hdf18mlkj11br AT 4ax DOT com...
> >> OUTCH! you believe this behavior is correct, too?
> >>
> >> OMG!
> >>
> >> ...and still no incorporation of   strrev(NO_ARGS);
> >>
> >> psst: that returns the last static value of a func, in this
> >> case, whatever the last string that was "reversed"
> >> (and no, its not a C++ thingy either; but all this is another story)
> >>
> >> On Sat, 29 Sep 2001 04:54:12 GMT, Les Cargill
> >> <lcargill AT worldnet DOT att DOT net> wrote:
> >>
> >> >Radical, let us look at what is meant by the code snippet:
> >> >printf("Original String: %s\nReversed String:%s\n", s, strrev(s));
> >> >
> >> >
> >> >First*, s is pushed on the stack, then "strrev" is called.
> >> >strrev reversed the original string in place.
> >> >
> >> >Next**, the pointer return from strrev, and s ( which *are the same
> >value* )
> >> >are both pushed on the stack
> >> >
> >> >Radical, NetSurfer wrote:
> >> >>
> >> >> On Sat, 29 Sep 2001 00:28:28 GMT, CBFalconer <cbfalconer AT yahoo DOT com>
> >> >> wrote:
> >> >>
> >> >> >"A. Sinan Unur" wrote:
> >> >> >>
> >> >> >> Radical NetSurfer wrote in
> >> >> >> news:lcq8rtk1nqua2hc6rqfhmqisbd587n8t2n AT 4ax DOT com:
> >> >> >>
> >> >> >> > I would like to encourage everyone who has a need for
> >> >> >> > strrev to come forward and encourage the maintainers of
> >> >> >> > LIBC used with GCC to kindly add   strrev.
> >> >> >>
> >> >> >> Count me against this if for no other reason that the fact that I
do
> >not
> >> >> >> like extra nonstandard function which solve tiny problems. If you
> >need the
> >> >> >> functionality, you can write one for your own situation. If it is
> >going to
> >> >> >> be added to a library, the solution needs to be useful to more
than
> >just
> >> >> >> one person in a particular situation.
> >> >> >>
> >> >> >> Anyway, the main point of my post, however, is to point out just
one
> >of the
> >> >> >> gotchas with these kinds of functions.
> >> >> >>
> >> >> >> You give the following usage example:
> >> >> >>
> >> >> >> > Example
> >> >> >> > printf("The reverse of %s is %s\n", str,  strrev(str) );
> >> >> >>
> >> >> >> Hmmmmm  ..... let us see using the code you suggested:
> >> >> >>
> >> >> >> /* +++Date last modified: 05-Jul-1997 */
> >> >> >> /*
> >> >> >> **  STRREV.C - reverse a string in place
> >> >> >> **
> >> >> >> **  public domain by Bob Stout
> >> >> >> */
> >> >> >>
> >> >> >> #include <string.h>
> >> >> >> #include <stdlib.h>
> >> >> >> #include <stdio.h>
> >> >> >>
> >> >> >> char *strrev(char *str) {
> >> >> >>         char *p1, *p2;
> >> >> >>
> >> >> >>         if (! str || ! *str) return str;
> >> >> >>         for (p1 = str, p2 = str + strlen(str) - 1; p2 > p1;
> >++p1, --p2)
> >> >> >>         {
> >> >> >>                 *p1 ^= *p2;
> >> >> >>                 *p2 ^= *p1;
> >> >> >>                 *p1 ^= *p2;
> >> >> >>         }
> >> >> >>         return str;
> >> >> >> }
> >> >> >>
> >> >> >> int main(void)
> >> >> >> {
> >> >> >>         char s[] = "This is a test.";
> >> >> >>         printf("Original String: %s\nReversed String:%s\n", s,
> >strrev(s));
> >> >> >>         return 0;
> >> >> >> }
> >> >> >>
> >> >> >> C:\var>gcc djstrrev.c -o djstrrev.exe -O2 -Wall
> >> >> >>
> >> >> >> C:\var>djstrrev
> >> >> >> Original String: .tset a si sihT
> >> >> >> Reversed String: .tset a si sihT
> >> >>
> >> >> If your compiler actually outputs both strings as reversed,
> >> >> THEN I am very scared your compiler is quite BROKEN.
> >> >>
> >> >> printf("format specifier1, format_specififer2", var1, func1);
> >> >>
> >> >> does:
> >> >> display __current__ value of   var1 FIRST using format_specifier1,
> >> >> __THEN__
> >> >> display __output__ of  funct1 using format_specifier2,
> >> >>
> >> >> If DJGPP is not doing even this trivial behavior correctly,
> >> >> Borland programs would never port correctly,
> >> >> neither would anything else for that matter.
> >> >>
> >> >> Left to right, in the order AND STATE ENCOUNTERED!
> >> >>
> >> >> ....however... __AFTER__ the call to   printf(), __THEN__
> >> >> 'str' will contain the result of the function call;
> >> >> but __NEVER__ from  __WITHIN__ the printf   as
> >> >> you implied.  Your post is VERY MISLEADING.
> >> >>
> >> >> >> Now, think about that.
> >> >> >
> >> >> >Thank you.  I knew there was a reason I made my equivalent
> >> >> >(revstring) a void function.  I just didn't know what it was :-)
> >>
> >
>