Random string? 1

[JRBeltman]

Hi all,
I found a nice piece of code on php.net.
It works well, but I do not understand all of this

for($len=10,$r='';strlen($r)<$len;$r.=chr(!mt_rand(0,2)?
mt_rand(48,57):(!mt_rand(0,1)?mt_rand(65,90):mt_rand
(97,122))));

Can anyone tell me what happens exactly in
(!mt_rand(0,2)?
mt_rand(48,57)!mt_rand(0,1)?mt_rand(65,90):mt_rand
(97,122)))

I am aware of the function of mt_rand, but do not understand this code :-(


JR
As a wise man once said: To build the house you need the stone.
Back to the Basics!

 

[sleipnir214]

I don't know who wrote that gobbledygook, and it may work, but it's a very bad coding style. It's unreadable and thus difficult to maintain. The author probably thought he was being cute.

Reformatting the segment as:

for
(
	$len=10,$r='';
	strlen($r)<$len;
	$r.=
		chr
		(
			!mt_rand(0,2)?
			mt_rand(48,57):
			(
				!mt_rand(0,1)?
				mt_rand(65,90):
				mt_rand(97,122)
			)
		)
);

You can see that whoever wrote that is using ghastly nested trinary operators to generate random numbers according to some kind of distribution.

The following code should be a functional equivalent:

$len = 10;
$r = '';

while (strlen($r) < $len)
{
	$a = mt_rand(0,2);

	if ($a != 0)
	{
		$a = mt_rand(48,57);
	}
	else
	{
		$a = mt_rand(0,1);

		if ($a != 0)
		{
			$a = mt_rand(65,90);
		}
		else
		{
			$a = mt_rand(97,122);
		}
	}

	$r .= chr($a);
}

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[JRBeltman]

very neat! for you.

Thanks

JR
As a wise man once said: To build the house you need the stone.
Back to the Basics!