From: neil AT robots DOT ox DOT ac DOT uk (Neil Townsend)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Optimizer and logical operators.
Date: Fri, 4 Sep 1998 12:10:57 GMT
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Message-ID: <1998Sep4.121057.1208@catorobots.ox.ac.uk>
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In comp.os.msdos.djgpp (SED AT ticnet DOT com) writes:
>So I should be able to rewrite:
>
>while( (*p1 != '\0') && isspace( *p1 ) )
>    ++p1;
>
>as
>
>while( (*p1 != '\0') && isspace( *(p1++) ) );

You could, but there would be a subtle change in functionality. In your
original code, p1 was incremented if the string hadn't ended and it pointed
to a spcae character. In the second line, p1 might be incremented one more
time: If the string hasn't ended and p1 point to a non-space character it
will still be incremented (because the increment is no longer conditional on
the success of the second clause). The loop will end in one of two ways:

1. The string is only space; p1 will point the the terminating chracter.
2. The string contains some non-space. The loop will terminate with p1
pointing to the character after the first non-space character (which will be
a '\0' if the string if there is only one non-space character followed by a
terminataing character.


eg

"       \0"  "     abcx\0"  "y\0"
        ^           ^         ^

Neil
-- 
Neil Townsend   +44 (1865) 273121   neil AT robots DOT ox DOT ac DOT uk