Calling an array of arrays in C. Post: 303023116

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Top Forums Programming Calling an array of arrays in C. Post 303023116 by apmcd47 on Wednesday 12th of September 2018 06:38:43 AM

09-12-2018

Registered User

The C programming language was not really designed with multi-dimensional arrays in mind. C sort of works with 2D arrays, but remember that they are either arrays of arrays or arrays of pointers to arrays. Get this wrong, and you will get lots of errors, or worse, segmentation faults.

3D arrays are a nightmare! Don't do it in C! Use a language better suited to multi-dimensional arrays, or an OO language with a tried-and-tested multi-dimensional array class. If you have to use C, don't use 3D arrays - emulate them instead!

Code:

typedef struct arr_str{
     int *arr;  /* pointer to array */
     int xDim; /* size of X dimension */ 
     int yDim; /* size of Y dimension */
     int zDim; /* size of Z dimension */
} threeDeeArr, *threeDeeArrPtr;

int getIndex(threeDeeArrPtr array, int x, int y, int z)
{
   int index;
   index = x * array.xDim;
   index = (index + y) * array.yDim;
   return index + z;
}

int getFromIndex(threeDeeArrPtr array, int x, int y, int z)
{
   return array->arr[getIndex(array, x, y, z)];
}

void putAtIndex(threeDeeArrPtr array, int x, int y, int z, int val)
{
   array->arr[getIndex(array, x, y, z)] = val;
}

my calculations of a 3D array are probably off, you will have to test that I got it right. The above code does not include the initialisation or destruction "methods" required before you can actually use this struct in anger. Once the indexing is correctly calculated the above struct will be much easier to use in C than proper 3D arrays.

Andrew

apmcd47

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LEARN ABOUT PHP

array_diff

ARRAY_DIFF(3)								 1							     ARRAY_DIFF(3)

array_diff - Computes the difference of arrays

SYNOPSIS

       array array_diff (array	$array1, array	$array2, [array  $...])

DESCRIPTION

	Compares $array1 against one or more other arrays and returns the values in $array1 that are not present in any of the other arrays.

PARAMETERS

	      o $array1
		- The array to compare from

	      o $array2
		- An array to compare against

	      o $...
		- More arrays to compare against

RETURN VALUES

	Returns an array containing all the entries from $array1 that are not present in any of the other arrays.

EXAMPLES

       Example #1

	      array_diff(3) example

	      <?php
	      $array1 = array("a" => "green", "red", "blue", "red");
	      $array2 = array("b" => "green", "yellow", "red");
	      $result = array_diff($array1, $array2);

	      print_r($result);
	      ?>

	       Multiple occurrences in $array1 are all treated the same way. This will output :

	      Array
	      (
		  [1] => blue
	      )

NOTES

       Note

	       Two  elements  are considered equal if and only if (string) $elem1 === (string) $elem2. In words: when the string representation is
	      the same.

       Note

	       This function only checks  one  dimension  of  a  n-dimensional	array.	Of  course  you  can  check  deeper  dimensions  by  using
	      array_diff($array1[0], $array2[0]);.

SEE ALSO

       array_diff_assoc(3), array_intersect(3), array_intersect_assoc(3).

PHP Documentation Group 													     ARRAY_DIFF(3)