Martin's Blog » multidimensional http://www.martienus.com Logic to Art Fri, 12 Feb 2010 19:07:38 +0000 en hourly 1 http://wordpress.org/?v=3.0.1 Check size constraints for multidimensional arrays http://www.martienus.com/code/check-size-constraints-for-multidimensional-arrays.html http://www.martienus.com/code/check-size-constraints-for-multidimensional-arrays.html#comments Mon, 08 Feb 2010 16:17:59 +0000 Martin http://www.martienus.com/?p=57 Multidimensional arrays are commonly used as a complex data structure. Moreover, they are used to convey data between software systems internally. In some programming languages however, there is no way to constrain the size of arrays at any stage of the array’s lifetime. PHP for instance has no ability to do this. Therefore a way must be devised to make sure the structure of the passed data conforms to what the receiving system expects.

Think for instance pixel convolution matrices. These are usually 3 by 3.

Check out my recursive PHP function to check sizes at any dimensional depth possible:

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function isDimension($arr, $dimensions)
{
   $pass = true;
   $amount = array_shift($dimensions);
 
   if($amount === -1 || count($arr) === $amount)
   {
      if(!empty($dimensions))
      {
         foreach($arr as $element)
         {
            if(is_array($element))
            {
               if(!isDimension($element, $dimensions))
               {
                  $pass = false;
               }
            }
            else
            {
               $pass = false;
            }
         }
      }
   }
   else
   {
      $pass = false;
   }
   return $pass;
}

And when we utilize this function in the following way:

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$subject = array(	array(1,2,3),
			array(2,3,4),
			array(3,4,5));
 
if(isDimension($subject, array(3,3)))
{
   print "Yay";
}
else
{
   print "Nay";
}

The output will be:

Yay

If at a certain dimension size does not matter you can skip it by entering -1 as the expected size:

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$subject = array(	array(1,2,3),
			array(2,3,4),
			array(3,4,5)
			array(4,5,6));
 
$wellIsIt = isDimension($subject, array(-1,3)); // Returns true
$wellIsIt = isDimension($subject, array(4,3)); // Returns true
$wellIsIt = isDimension($subject, array(3,3)); // Returns false

This is a recursive function, meaning that it calls itself from within itself until a certain condition is met. Then it cascades the result back to the initial function call which in turn passes it back to whatever script called the function. More about this can be read on wikipedia.

There ya go

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