Loop not working correctly (floats and integer issue?) -- PHP

Question

The code below generates two random decimal values, then subtracts them to get $c.

The do-while loop is trying to ensure that $c will not be a whole number. But I keep getting times where $c actually is a whole number.

        do{
            unset($a);
            unset($b);
            unset($c);
            unset($adjuster);
            unset($c_is_int);

            $a = mt_rand(5, 75);
            $b = mt_rand(5, 75);
            $adjuster = mt_rand(2, 20);

            $decimal_selector = mt_rand(1, 6);
            if ($decimal_selector == 1){
                $a = $a / 10;
                $b = $b / 10;
            }
            if ($decimal_selector == 2){
                $a = $a / 10;
                $b = $b / 100;
            }
            if ($decimal_selector == 3){
                $a = $a / 100;
                $b = $b / 10;
            }
            if ($decimal_selector == 4){
                $a = $a / 100;
                $b = $b / 100;
            }
            if ($decimal_selector == 5){
                $a = $a / 1000;
                $b = $b / 1000;
            }
            if ($decimal_selector == 6){
                $a = $a / 1000;
                $b = $b / 100;
            }

            if($b < $a){
                $b = $b + ($a - $b) + $adjuster;
            }

            $c = $b - $a;

            if(intval($c) == $c) {
                $c_is_int = 1;
            } else {
                $c_is_int = 0;
            }

echo $a . '<br><br>';
echo $b . '<br><br>';
echo intval($c) . '<br>';
echo $c_is_int . '<br>';
echo $c . '<br><br>';
        } while($c_is_int == 1);

The attached image shows the results of one of these failing times. Any ideas on where this is going wrong?

enter image description here

It's still not clear what the purpose of your code is. Not implausible that you're looking for e.g. [arbitrary precision math](http://www.php.net/manual/en/book.bc.php) though instead of float/int juggling. — mario, Dec 04 '13 at 02:04

score 0 · Accepted Answer · answered Dec 04 '13 at 01:58

0

Why not check to see if the number has a decimal?

$c = 123.456;

if(strpos((string) $c, '.') !== FALSE) {
    // is decimal/float/double
}

You can also just check to see if it's an int

if(is_int($c))

answered Dec 04 '13 at 01:58

Xeoncross

55,620
80
262
364

I originally tried `is_int()`, but it kept failing for some reason (http://stackoverflow.com/questions/20364384/double-integer-php/20364537) – gtilflm Dec 04 '13 at 02:02

score 0 · Answer 2 · answered Dec 04 '13 at 01:59

0

You want to keep in mind that the integer 3 and float 3.0 will compare as equal when using the ==.

Consider:

$c_is_int = $c == floor( $c );
...
while( $c_is_int )

answered Dec 04 '13 at 01:59

Matt R. Wilson

7,268
5
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48

Loop not working correctly (floats and integer issue?) -- PHP

2 Answers2

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