Fun alternative. A tad dangerous, though, not because of your use of commas but because your code could suffer from integer overflows.

@manveru –

Right. What was I thinking? I guess I could use an anonymous function to create a new scope but then the swapped result would only live in that other scope, right? (You may have guessed that my knowledge of Erlang is very superficial so far)

@anonymous –

“But that’s cheating!” he whined

int a = 1;
int b = 27;

a = b – a, b = b – a, a = a + b;

Hmf I realized, after re-reading your test harness, that the amount of parsing should be the same. Shame on me.

Ha! I do not think that I would have bothered writing a test harness for PHP’s assignment. And, apparently, I would have been wrong: your results are surprising since they show that parsing more code will, in the end, be as fast as calling a built-in function.

<?php
$time_start = microtime(true);
$i =0;

do
{
$a = 1;
$b = 2;
list($a, $b) = array($b, $a);
}while(++$i < 100000);

$time_end = microtime(true);
$time = $time_end – $time_start;

echo ‘Test 1: ‘,$time,”;

$time_start = microtime(true);
$i =0;

do
{
$a = 1;
$b = 2;
$x = $a;
$y = $b;
$a = $y;
$b = $x;
unset($x, $y);
}while(++$i < 100000);

$time_end = microtime(true);
$time = $time_end – $time_start;

echo ‘Test 2: ‘,$time,”;

$time_start = microtime(true);
$i =0;

do
{
$a = 1;
$b = 2;
$x = $a;
$y = $b;
$a = $y;
$b = $x;
}while(++$i < 100000);

$time_end = microtime(true);
$time = $time_end – $time_start;

echo ‘Test 3: ‘,$time,”;

unset($x, $y);
echo ‘a=’,$a’, b=’,$b,”\n”;

Would be interesting to do a test of speed and memory usage between the two.