Is it possible to determine amount of rows of a 2-d array passed in a function

hugo2x · 11-10-2009, 04:45 PM

I am trying to make a function that accepts a an array by reference and determines the amount of rows in the 2-d array.
Is there a way to do this? (I do know the columns)

Code:

void printer(int [][3]);
int main(void)
{
	int array1[][3]={{ 5,9, 0},
			{14,7,13},
	                 { 2,10,8}};
	int array2[][3]={{ 5,9, 0},
	                 {14,7,13},
                          {55,10,9}
	                  { 2,10,8}};
	
	printer(array1);
        printer(array2);
}

void printer(int ary[][3])
{
	int rows = ////// some way to calculate 3 from first instance and 4 for second instance, I have tried sizeof(array)/sizeof(int) but it only calculates the size of the address of array(0Xff244da) */
	
}

Any help would greatly be appreciated!

King Mir · 11-10-2009, 05:02 PM

If by rows you mean the first dimension of the array, that is omitted from the deceleration, then there is no way given the prototype. You can do this:

Code:

void printer(int (*ary)[4][3])//pointer to 4x3 array
{
        int cols = sizeof(**ary)/sizeof(***ary);
        /*size of each row devided by the size of each element in each row. (sizeof(***ary)==sizeof(int))
        cols should equal 3.*/
	int rows = sizeof(*ary)/sizeof(**ary); 
        /*This computes the size of the whole array divided by the size of each row.
        rows should equal 4.*/
	(*ary)[1][1]=5;/*this is how to access the array. */
        ary[0][1][1]=5;/*this is also valid */
}

It's not as ugly in C++.

Adak · 11-10-2009, 05:35 PM

Could you just pass both dimensions? There had to be a variable for the rows when you put the data into the array.

11-10-2009, 04:45 PM	#1
hugo2x Registered User Join Date: Sep 2009 Posts: 13	Is it possible to determine amount of rows of a 2-d array passed in a function I am trying to make a function that accepts a an array by reference and determines the amount of rows in the 2-d array. Is there a way to do this? (I do know the columns) Code: void printer(int [][3]); int main(void) { int array1[][3]={{ 5,9, 0}, {14,7,13}, { 2,10,8}}; int array2[][3]={{ 5,9, 0}, {14,7,13}, {55,10,9} { 2,10,8}}; printer(array1); printer(array2); } void printer(int ary[][3]) { int rows = ////// some way to calculate 3 from first instance and 4 for second instance, I have tried sizeof(array)/sizeof(int) but it only calculates the size of the address of array(0Xff244da) / } Any help would greatly be appreciated! Last edited by hugo2x; 11-10-2009 at 04:55 PM.*
hugo2x is offline

11-10-2009, 05:02 PM	#2
King Mir Registered User Join Date: Apr 2006 Posts: 1,193	If by rows you mean the first dimension of the array, that is omitted from the deceleration, then there is no way given the prototype. You can do this: Code: void printer(int (ary)[4][3])//pointer to 4x3 array { int cols = sizeof(ary)/sizeof(*ary); /size of each row devided by the size of each element in each row. (sizeof(**ary)==sizeof(int)) cols should equal 3./ int rows = sizeof(ary)/sizeof(ary); /This computes the size of the whole array divided by the size of each row. rows should equal 4./ (ary)[1][1]=5;/this is how to access the array. / ary[0][1][1]=5;/this is also valid / } It's not as ugly in C++. __________________ It is too clear and so it is hard to see. A dunce once searched for fire with a lighted lantern. Had he known what fire was, He could have cooked his rice much sooner. Last edited by King Mir; 11-10-2009 at 05:24 PM.
King Mir is offline

11-10-2009, 05:35 PM	#3
Adak Registered User Join Date: Sep 2006 Posts: 2,502	Could you just pass both dimensions? There had to be a variable for the rows when you put the data into the array.
Adak is offline

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