Two Dimensional Arrays

[Lock]

I am very new to C and am getting an error and a warning that I am not sure how to fix. I am very prone to problems with declarations and especially the types in declarations so I am fairly sure that is what my problem is. Here is the code:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#define BOARD_SIZE 4

void initial_board (char board [], int board_size);

int
main ()
{

  char board[BOARD_SIZE][BOARD_SIZE];
  initial_board (board, BOARD_SIZE);

  return 0;
}

void
initial_board (char board [], int board_size)
{
  int i, j;
  for (i = 0; i < board_size; i++)
    {
      for (j = 0; j < board_size; j++)
    {
      board[i][j] = '.';
    }
    }
  for (i = 0; i < board_size; i++)
    {
      for (j = 0; j < board_size; j++)
    {
      printf ("%\t", board[i][j]);
    }
      printf ("\n");
    }
}

What I get when compiling:

warning: passing argument 1 of "initial_board" from incompatible pointer type.
occurs at: initial_board (board, BOARD_SIZE);
note: expected "char *" but argument is of type "char (*)"
occurs at: oid initial_board (char board [], int board_size);
error: subscripted value is neither array nor pointer
occurs at: board[i][j] = '.';
error: subscripted value is neither array nor pointer
occurs at: printf ("%\t", board[i][j]);

Thanks for any help!

[quzah]

Why would you think that would work?

void initial_board (char board [], int board_size);
 
int
main ()
{
 
  char board[BOARD_SIZE][BOARD_SIZE];
  initial_board (board, BOARD_SIZE);

board has 2 dimensions, but your function expects an array that only has one dimension.


Quzah.

[Lock]

Ahh yes, that was quite a silly mistake. However, changing

initial_board (char board[], int board_size)

to

initial_board (char board[][], int board_size)

gives me an error of "array type has incomplete element type" even though I want all of the elements of the two dimensional array to be chars.

[anduril462]

C only allows you have have the leftmost set of brackets empty. You need to put the dimension in the right brackets, like char board[][BOARD_SIZE].

[rmatze]

When passing a multidimensional array in this manner, only the first dimension can be omitted.

Try:

void initial_board (char board[][BOARD_SIZE], int board_size)

Also you don't have to pass board_size because you defined it.

[TheBigH]

The reason for this is that a, say, 50x30 array is stored in memory as 1,500 consecutive elements. If you pass the array to a function, how can the function know it's a 50x30 array and not 30x50 or 15x100 or 3x500 if you don't tell it what the dimensions are?

[Lock]

Thanks for clearing that up guys. I fixed it and it makes sense. One other quick question that I had though was in terms of returning multiple values. For this program I want to take in a user's input several times and then use that input to manipulate that spot in the array. So I scanf in x and y values for the player's move each turn but how do I return these values from my scanning function so that I can manipulate them in other functions? I know I can't return multiple values, so should I just use pointers for the x and y values and then manipulate them in other functions through the pointers?

[CommonTater]

Yes, you will have to do that with pointers...