Swap an array...

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Join Date: Nov 2006

Location: Athens, Greece

Posts: 198

Reputation: n.aggel is an unknown quantity at this point

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Solved Threads: 9

n.aggel

Offline

Junior Poster

Swap an array...

May 16th, 2008

hi guys, it's been a while since i used c for anything so here goes a question tha may seem silly.

I have 2 variable length arrays....

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
 
int main()
{
	int n = 5;
	int m = 6;
 
	int before[n][m];
	int after[n][m];
	array_function( 5, 6, before, after );
}
 
void array_function(int rows, int cols, float after[rows][cols] , float before[rows][cols])
{
	//for some iterations	
	for(;;)
	{
 
		//for all the elements int the array
		for (i=1; i<rows; i++)
			for(j=1; j<cols; j++)
				after[i][j] = 4 * before[i][j]
 
		//afterwards prepare for the next iteration [1]
		for (i=1; i<rows; i++)
			for(j=1; j<cols; j++)
				before[i][j]=after[i][j];
	}
}
 
int main()
{
	int n = 5;
	int m = 6;

	int before[n][m];
	int after[n][m];
	array_function( 5, 6, before, after );
}

void array_function(int rows, int cols, float after[rows][cols] , float before[rows][cols])
{
	//for some iterations	
	for(;;)
	{

		//for all the elements int the array
		for (i=1; i<rows; i++)
			for(j=1; j<cols; j++)
				after[i][j] = 4 * before[i][j]

		//afterwards prepare for the next iteration [1]
		for (i=1; i<rows; i++)
			for(j=1; j<cols; j++)
				before[i][j]=after[i][j];
	}
}

...What i want to do is find a way to swap the pointers to the arrays. So that i can get rid of the last loop.
I figured that since i only need to calculate "after" based on "before" and then make "after"->"before" and recalculate "after".
It would save a lot of time if i just swapped the 2 pointers.

i tried the following but with no luck:

 Help with Code Tags 
 c Syntax (Toggle Plain Text) 
//define function like this:
void array_function(int rows, int cols, float &after[rows][cols] , float &before[rows][cols])
 
//call it like this:
array_function( 5, 6, &before, &after );
//define function like this:
void array_function(int rows, int cols, float &after[rows][cols] , float &before[rows][cols])

//call it like this:
array_function( 5, 6, &before, &after );

thanks in advance
-nicolas

Two roads diverged in a wood, and I— I took the one less traveled by, and that has made all the difference.

by Robert Frost the "The Road Not Taken"