Tom Phoenix wrote:
On 10/19/06, Norbert Preining <[EMAIL PROTECTED]> wrote:
$b = (++$a) + ($a++);
I'm not sure whether C does so, but I believe that Perl does NOT
promise that auto-increments will be executed in the "expected"
left-to-right order. Thus, if a single expression includes more than
one auto-increment working on the same variable, generally you can't
be sure what Perl will do with it. As you found.
Did this come up in a real-world situation, or were you specifically
seeking to test the limits of Perl? In other words, what problem, if
any, are you trying to solve?
I think it's academic Tom, and it's caught my interest!
The order of evaluation is immaterial, look:
$a = 3;
$b = 0;
$b += ++$a; # Now $a == 4, $b == 4
$b += $a++; # Now $a == 5, $b == 8
$a = 3;
$b = 0;
$b += $a++; # Now $a == 4, $b == 3
$b += ++$a; # Now $a == 5, $b == 8
so the final values of $a and $b are the same regardless and Perl is definitely
doing something wrongly in the single-line version. Although it's clearly not
a very important thing since it's managed to remain unfixed since at least
v5.6 if not before!
Cheers,
Rob
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