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Top Forums Programming Making an array of 2D arrays in C Post 303021771 by Corona688 on Thursday 16th of August 2018 12:46:45 PM
Old 08-16-2018
int * isn't enough information for C to know what kind of array is being pointed to. That assumes a single integer or 1D array.

int *matrix[size][size] does not make pointers to 2d arrays -- it makes a 2d array of pointers.

Pointing to an array of known size takes this slightly wonky syntax:

int (*variablename[size][size]) [elements];

The stuff inside the red brackets defines the array being pointed to, the [elements] outside it defines the actual number of elements.

An example:

Code:
int main(void)
{
        int arr2d[2][2]={ {1,2},{3,4} };
        int arr2db[2][2]={ {5,6},{7,8} };

        int (*ptr[2][2])[2]= { arr2d, arr2db };
}

I thank @yifangt for pointing out to me this was even possible. C has a few weird corners.

Last edited by Corona688; 08-16-2018 at 05:16 PM..
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ARRAY_DIFF_ASSOC(3)							 1						       ARRAY_DIFF_ASSOC(3)

array_diff_assoc - Computes the difference of arrays with additional index check

SYNOPSIS
array array_diff_assoc (array $array1, array $array2, [array $...]) DESCRIPTION
Compares $array1 against $array2 and returns the difference. Unlike array_diff(3) the array keys are also used in the comparison. 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 values from $array1 that are not present in any of the other arrays. EXAMPLES
Example #1 array_diff_assoc(3) example In this example you see the "a" => "green" pair is present in both arrays and thus it is not in the output from the function. Unlike this, the pair 0 => "red" is in the output because in the second argument "red" has key which is 1. <?php $array1 = array("a" => "green", "b" => "brown", "c" => "blue", "red"); $array2 = array("a" => "green", "yellow", "red"); $result = array_diff_assoc($array1, $array2); print_r($result); ?> The above example will output: Array ( [b] => brown [c] => blue [0] => red ) Example #2 array_diff_assoc(3) example Two values from key => value pairs are considered equal only if (string) $elem1 === (string) $elem2 . In other words a strict check takes place so the string representations must be the same. <?php $array1 = array(0, 1, 2); $array2 = array("00", "01", "2"); $result = array_diff_assoc($array1, $array2); print_r($result); ?> The above example will output: Array ( [0] => 0 [1] => 1 ) NOTES
Note This function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using, for example, array_diff_assoc($array1[0], $array2[0]);. Note Ensure you pass arguments in the correct order when comparing similar arrays with more keys. The new array should be the first in the list. SEE ALSO
array_diff(3), array_diff_uassoc(3), array_udiff_assoc(3), array_udiff_uassoc(3), array_intersect(3), array_intersect_assoc(3). PHP Documentation Group ARRAY_DIFF_ASSOC(3)
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