Conways Game using Pointers

[NewUser]

Hi,
I am new to C programming language. I am trying to rewrite the code on Conways game of life using pointers. The current piece of code without pointers is this:

static void
evolve(char arena[WIDTH][HEIGHT])
{
	int x, y;
	
	// First shift each cell to the left so its occupied status
	// is in bit 1 rather than bit 0
	for (x = 0; x < WIDTH; x++)
		for (y = 0; y < HEIGHT; y++)
		{
			printf("\nx is %d, y is %d arena value is %d\n",x,y,arena[x][y]);
			arena[x][y] <<= 1;
		}

	// Decide whether each cell should be occupied based on the
	// number of previously occupied neighbours etc.
	for (x = 0; x < WIDTH; x++)
		for (y = 0; y < HEIGHT; y++) {
			int neighbours = 0;

			neighbours += WAS_OCCUPIED_ANY(arena, x - 1, y - 1);
			neighbours += WAS_OCCUPIED_ANY(arena, x - 1, y);
			neighbours += WAS_OCCUPIED_ANY(arena, x - 1, y + 1);
			neighbours += WAS_OCCUPIED_ANY(arena, x, y - 1);
			neighbours += WAS_OCCUPIED_ANY(arena, x, y + 1);
			neighbours += WAS_OCCUPIED_ANY(arena, x + 1, y - 1);
			neighbours += WAS_OCCUPIED_ANY(arena, x + 1, y);
			neighbours += WAS_OCCUPIED_ANY(arena, x + 1, y + 1);
			if (neighbours == 3 || (neighbours == 2 && WAS_OCCUPIED_ANY(arena,x,y)))
				arena[x][y] |= 1;
		}
}

The above function is the evolve part of the game and it works well. I am trying to use pointers to dynamically allocate and set the array using malloc.

Can anyone help? pls!

Thanks.

[whiteflags]

Yes. How much have you read about pointers? Can you explain what you don't understand?

[NewUser]

I know we have to use malloc to initialise the memory dynamically. Before evolving each step we have to create the memory and initialise it. I am not sure where to start. I am bit familiar with the concepts.

Thanks for the tutorial link. I revised the concepts.

[whiteflags]

You can use pointers to simulate arrays. I noticed that the tutorial linked earlier does not go into that, but other sources would. From what you've told me, you need more reading on that subject. So look for things detailing multidimensional array building and reallocation.

[Adak]

I wouldn't realloc anything in Conways Game of Life, because the board or grid, stays the same size, throughout the game.

This is an example, that may be relevant to what you want:

#include <stdio.h>
#include <stdlib.h>

//we can pass this way without knowing the values of max rows and columns
//we could change it, if we knew the sizes at this point

void print(char**, int, int);

int main(void) {
	
   char **grid;          //2D arrays get two *'s
   int i, j;
   int max_rows = 3;     //these values could also come from the user
   int max_columns = 3;

   /* note that the sizeof, is to a *pointer* of the data type, not the data type size, itself */
   *grid = malloc(max_rows * sizeof(char*));  //getting memory for the 1st dimension
                                      

   /* getting memory for each row (2nd dimension), sized for the data type, not a pointer */
   for(i = 0; i < max_rows; i++)
      grid[i] = malloc(max_columns * sizeof(char));  
   	
	for(i = 0; i < max_rows; i++){
		for(j = 0; j < max_columns; j++){
			grid[i][j] = 'X';
		}
	}
	
	print(grid, max_rows, max_columns);

   //free the 2nd dimension (each row), first
   for(i = 0; i < max_rows; i++)
      free(grid[i]);

   //then free the 1st dimension of the array
   free(grid);

   printf("\n\n\t\t\t      press enter when ready ");
   i = getchar();
   return 0;
}

void print(char **grid, int max_rows, int max_columns) {
   int i, j;	
	
   for(i = 0; i < max_rows; i++){
      for(j = 0; j < max_columns; j++){
         printf("%c ", grid[i][j]);
      }
      printf("\n");
   }
}

[NewUser]

Thank you Adak. I am working on it. If i get any doubts, will come back and ask. Thank you.

[NewUser]

The load function has already set the initial array.

The code I tried to implement in evolve function is this: its giving me a wrong output....can anyone tell where my logic is wrong pls:

/*  Evolve a life arena by one generation.  The array arena should
 *  have length width with each entry representing a column of
 *  cells.  Columns that are empty should be NULL when the function is called
 *  and on return.  Columns that have some occupied cells should be a
 *  malloc'ed character array of length height.  Individual cells that
 *  are occupied should have their RH bit = 1 and empty cells should have 
 *  their RH bit = 0.
 */
void
evolve(char **arena, int width, int height)
{
	int x,y;
	int i=0;
	
	for(x=0;x<width;x++)
		if(arena[x]!=NULL)
	for(y=0;y<height;y++) {
		if(arena[x][y]!= NULL)
			arena[x][y] <<= 1;
		else 
			arena[x][y] = arena[x][y] & 0;
			//printf("\narena  = %d %d %d", arena[x][y], x,y);
	}
	
	for(x=0;x<width;x++)
	for(y=0;y<height;y++) {
		int neighbours = 0;
		
		// if the column cell is occupied
		if(arena[x]!=0) {
		//	printf("\nx = %d y = %d", x,y);
		//	getchar();
			if(arena[x-1]!=0) {
//				printf("did this enter");
//				getchar();
				neighbours+= WAS_OCCUPIED_ANY(arena, x-1,y);
				neighbours+= WAS_OCCUPIED_ANY(arena, x-1,y-1);
				neighbours+= WAS_OCCUPIED_ANY(arena, x-1,y+1);
//				printf("neighbours = %d", neighbours);
			}
			
			if(arena[x+1]!=0) {
//				printf("did this enter\n");
//				getchar();
				neighbours+= WAS_OCCUPIED_ANY(arena, x+1,y);
				neighbours+= WAS_OCCUPIED_ANY(arena, x+1,y-1);
				neighbours+= WAS_OCCUPIED_ANY(arena, x+1,y+1);
//				printf("neighbours = %d\n", neighbours);
			}
			
			neighbours+= WAS_OCCUPIED_ANY(arena, x,y-1);
			neighbours+= WAS_OCCUPIED_ANY(arena, x,y+1);
						
			if(neighbours==3 || neighbours==2 || IS_OCCUPIED(arena,x,y) ) {				
				arena[x][y]|=1;
			} else if (neighbours > 3 || neighbours < 2) { 
				arena[x][y]=0; int check = 0;
				for(i = 0;i < height; i++) {
					if(!(arena[x][i]==0)) {
						check = 1;
					}
					if(check == 0) {
						free(arena[x]);
					}
				}
			}
		} else if(arena[x]==0) { // if the column cells are not occupied
			if(arena[x-1]!=0) {
				neighbours+= WAS_OCCUPIED_ANY(arena, x-1,y);
				neighbours+= WAS_OCCUPIED_ANY(arena, x-1,y-1);
				neighbours+= WAS_OCCUPIED_ANY(arena, x-1,y+1);
			}
			
			if(arena[x+1]!=0) {
				neighbours+= WAS_OCCUPIED_ANY(arena, x+1,y);
				neighbours+= WAS_OCCUPIED_ANY(arena, x+1,y-1);
				neighbours+= WAS_OCCUPIED_ANY(arena, x+1,y+1);
			}
			
			if(neighbours==3 || neighbours==2) {
				arena[x] = malloc(height);
				for(i=0;i<height;i++)
					arena[x][i]=0;
				arena[x][y]|=1;
			}
		}

[MK27]

....can anyone tell where my logic is wrong

Yep.

1) "Giving me a wrong output" IS NOT a sufficient description of your problem. What is wrong with the output?
2) If you get compiler errors or warnings, or runtime errors, you need to describe those too.
3) You posted without code tags. Do not pass GO. Do not collect $200. Fix it now.

[NewUser]

The cellular generation is not showing accordingly, there is a logical error. What is a code tag?
and the macros are fine, its just the logical error in code. I dont know how to fix it.

I tried to change to a smaller version, but it has logical error too..

<<< HORRIBLE CODE DELETED >>>

the above version the latest.

Any solutions for either of the two versions plsssssssssssss?

Thanks in advance.

[MK27]

What is a code tag?

You used them in your earlier post.

Code goes here.

<< !! Posting Code? Read this First !! >>

[quzah]

You used them in your earlier post.

No, Salem added them. See the edit?

[code]
... put code here ...
[/code]


Quzah.