Recursion

[web4]

<?php

 

function getGCF($a,$b) {

echo "$b<br />";

if($b==0)

  return $a;

else

  return getGCF($b,$a % $b);

}

 

echo getGCF(6,10)."answer<br />";

 

?>

 

10

6

4

2

0

2answer

10

6

4

2

0

 

My problem is why did 10,6,4,2,0 appear?? i thought the output would be 0,2,4,6,10 cause that's the way recursion works....like in this example..

 

function nfact($n)

{

  if ($n == 0)

  {

    return 1;

  }

  else

  {

    return $n * nfact($n - 1);

  }

}

 

the way the recursion works in that program is they return the previous value of the function and that was my expectation in the first script...how did that happen? thanks

 

[Mchl]

When debugging cases like this, it's useful to keep track of what your function does step bt step

getGCF(6,10)        $a = 6;  $b = 10; -> echo $b prints '10'; getGCF(10, 6%10) is called

getGCF(10, 6%10)    $a = 10; $b = 6;  -> echo $b prints '6'; getGCF(6,10%6) is called

getGCF(6,10%6)      $a = 6;  $b = 4;  -> echo $b prints '4'; getGCF(4,6%4) is called

getGCF(4,6%4)        $a = 4;  $b = 2;  -> echo $b prints '2'; getGCF(2,4%2) is called

getGCF(2,4%2)        $a = 2;  $b = 0;  -> echo $b prints '0'; 2 is returned

[web4]

Yes i know that...actually if you run that code...only the upper part will appear... i've didn't post the other codes...i solved it on my own...anyways thanks for the reply