[Resolved] make a number plus or minus randomly

fr8

only way i could think of is this:
$TheNumber = 500;

$rand = rand(0,1);
if($rand == 1){
$TheNumber= '-'.$TheNumber.'';
}

This works but i have serveral numbers to do this with. and this would equal alot of code to make 3 numbers plus or minus. any other way to do this?

Installer

You could shorten it to this:

if ($rand = rand(0,1)) { 
    $num = '-' . $num;
}

Or you could put it into a function (cutting down on repetitive code is one of the functions of functions):

function rand_sign($num)
{
    if ($rand = rand(0,1)) { 
        $num = '-' . $num;
    }
    return $num; 
}

$number = rand_sign($number);

Or you could do this, in or out of a function:

$signs = array('-', '+');
$number = $signs[rand(0, 1)] . $number;

fr8

why doesnt this equal just a number?

$signs = array('-', '+');
$hp_p=10;
$hp_p_rn=rand(1,10);

$new = $hp_p . $signs[rand(0, 1)] . $hp_p_rn;

bradgrafelman

The period concatenates a string, meaning it glues the two pieces together.

Concatenation is used for the sign and the number, because what you're doing is taking a plus or minus sign and attaching it to a number. The "$hp_p ." part you used is essentially glueing that number onto the sign and the number, when instead we want to add the two numbers together. Try this:

$signs = array('-', '+'); 
$hp_p=10; 
$hp_p_rn=rand(1,10); 

$new = $hp_p + ($signs[rand(0, 1)] . $hp_p_rn);

I grouped the sign and the random number together so that PHP knows it should do that first, kind of like the order of operations in a math problem. Now that PHP has concatenated (or glued together) the sign and the random number, it then adds the two numbers together, resulting in another number since its a simple math addition problem.

I hope I explained it well enough that you can make some sense out of it now, lol.

fr8

what i was trying to do was have the number add/minused. im looking at just make the +/- random in the formula.

bradgrafelman

I know... that's why I pointed out the error you made and showed you the correct code...

Installer

why doesnt this equal just a number?

Because it's just a string; that's what it will be implicitly cast to when you use the concatenation operator. If you want to do arithmetic, you need to use the operator itself (otherwise it's too much like overloading, I guess).

You could use that implicit type casting to get it done like this:

$new = $hp_p + ($signs[rand(0, 1)] . $hp_p_rn);

Edit: Just like Brad said.

fr8

im rockin now. thanks.

laserlight

actually, why concatenate?
We're dealing with numbers, and concatenation is for strings.

function randSign($num) {
	return (mt_rand(0, 1)) ? $num : -$num;
}
//e.g.
echo randSign(2);