Function to return prime factors

[748323]

Grr.. I've been trying to figure this out for a few days now, but I can't figure it out. I've been into PHP for about 6 months now, so I know the functions needed. I just can't convert it into code.

Here is a function I made to return the first pair of factors that isn't 1 or the number. 20 would return 2-10

<?

function firstfactor($num) {
	for ($i=2; $i <= $num/2; $i++) {
		if (($num/$i) == floor($num/2)) {
			return $i . '-' . $num/$i;
		}
	}
}
?>

I also made a function to check if a number is prime, a decimal, and a function that returns all factors.

Can you help me out a bit? Please, no PHP code. I would rather just have a hint pointing me in the right direction mentally. Thanks!

 

[748323]

Wait. Let me try this. I know I can do it. I'll run back here if I can't do it by tonight.

 

[748323]

Err.. I can't do it. I tried, but can't. Help is welcomed. Thanks.

 

[jpadie]

wotcha - what's the actual problem? that it's not returning what you want?

 

[jpadie]

i see. it doesn't work for odd numbers!

without providing php code, and sticking with the logic of your code, surely once $i is fully incremented and no result is found, you need to increment the divisor of $num and restart the if loop. reductor ad finitum if no answer you have a prime.

hth
Justin

 

[748323]

I need to do this by myself. I'll keep trying. Its just going to click one day.

 

[748323]

I did it!

Never give up.

 

[jpadie]

are you going to post the result. so far this post is pretty much an existentialist monologue!

 

[DRJ478]

Err... jpadie you are right. To be or not to be...