Computer Science Canada Basic Prime Function Help |
| Author: | compstudent [ Tue Mar 15, 2011 9:20 pm ] |
| Post subject: | Basic Prime Function Help |
Hi, I am just starting learning PHP and I have tried to make this Prime Number function. I know it is redundant and not efficient. It also has a little HTML form, but whenever I run the function it says you cannot divide by zero in a big error box on the web browser (through easyPHP) Here is the code function findPrime($number) { $no=true; $i=2; while($i<$number) { if ($number % $i = 0) { $no=false; return $no; } $i++; } if ($no != false) { $no=true; return $no; } } if (findPrime($num1)) { echo $num1 . " is a prime number."; } else { echo $num1 . " is not a prime number."; } if (findPrime($num2)) { echo $num2 . " is a prime number."; } else { echo $num2 . " is not a prime number."; } Thanks! |
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| Author: | apython1992 [ Wed Mar 16, 2011 8:53 am ] |
| Post subject: | RE:Basic Prime Function Help |
I'll admit I've never used PHP before, but a quick google search tells me that the comparison operator '==' is used to test for equality, like many other languages. You instead used '=', which actually assigns the value 0 to $i, resulting in the zero division error. Aside from this, I think you'll quickly discover that your function won't actually correctly determine whether or not a number is prime. But that's okay! Learning is a good thing, and you can find lots of help here. |
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| Author: | DemonWasp [ Wed Mar 16, 2011 9:12 am ] |
| Post subject: | RE:Basic Prime Function Help |
PHP has some wacky rules on operator precedence. See here for details: http://www.tuxradar.com/practicalphp/3/12/7 Long story short, the expression "$number % $i = 0" is evaluated as "$number % ( $i = 0 )", even though you meant "($number % $i) == 0". |
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| Author: | compstudent [ Wed Mar 16, 2011 1:26 pm ] |
| Post subject: | Re: Basic Prime Function Help |
Okay - thats good to know- thanks a lot. |
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