Pointer for 2D array seems to be 3D in C Post: 302999280

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Top Forums Programming Pointer for 2D array seems to be 3D in C Post 302999280 by Corona688 on Friday 16th of June 2017 11:13:22 AM

06-16-2017

Registered User

1) They probably differ in being constants or non-constants.

3) It's "3d" because you have an extra pointer in the way. Every level of pointers requires another dereferencing operation to access it. One level pointer requires one. Two level pointer requires two. Three level pointer requires three. 97 level pointer requires 97. That is the pattern.

The first dereferencing operation gets rid of is x itself; once you do so, you are essentially accessing y. The next level of pointers points to individual rows inside y. The last level gets you an individual cell in that row.

Code:

x; // pointer to Y
(*x); // Y, i.e. pointer to rows
(*x)[0]; // Pointer to row 0
(*x)[0][0] // Row 0 col 0.  No longer a pointer.

The diagram is x -> y -> row -> column.

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LEARN ABOUT PHP

key

KEY(3)									 1								    KEY(3)

key - Fetch a key from an array

SYNOPSIS

       mixed key (array  &$array)

DESCRIPTION

       key(3) returns the index element of the current array position.

PARAMETERS

	      o $array
		- The array.

RETURN VALUES

	The  key(3)  function  simply  returns the key of the array element that's currently being pointed to by the internal pointer. It does not
       move the pointer in any way. If the internal pointer points beyond the end of the elements list or the array is empty, key(3) returns NULL.

EXAMPLES

       Example #1

	      key(3) example

	      <?php
	      $array = array(
		  'fruit1' => 'apple',
		  'fruit2' => 'orange',
		  'fruit3' => 'grape',
		  'fruit4' => 'apple',
		  'fruit5' => 'apple');

	      // this cycle echoes all associative array
	      // key where value equals "apple"
	      while ($fruit_name = current($array)) {
		  if ($fruit_name == 'apple') {
		      echo key($array).'<br />';
		  }
		  next($array);
	      }
	      ?>

	      The above example will output:

	      fruit1<br />
	      fruit4<br />
	      fruit5<br />

SEE ALSO

       current(3), next(3).

PHP Documentation Group 														    KEY(3)