Reading in a 2D array as an argument in a function in C++?

Question

i'm trying to pass a 2D char array into a function declared in a header file.

//Proj1Aux.h

#ifndef PROJ1AUX_H
#define PROJ1AUX_H

void makeBoard(char (*myBoard)[10], int boardSize);
void printBoard(char (*myBoard)[10], int boardSize);

#endif

I defined the functions as follows:

//Proj1Aux.cpp

#include <iostream>
#include "Proj1Aux.h"

using namespace std;

void makeBoard(char (*myBoard)[10], int boardSize)
{
    //code
}

void printBoard(char (*myBoard)[10], int boardSize){

    //code
}

And then in my main function in another .cpp file:

//Proj1.cpp


#include <iostream>
#include <cstdlib>
#include "Proj1Aux.cpp"

using namespace std;

int main(int argc, char* argv[]){

    //code...
    //more code...

    char board[10][10];
    makeBoard(board, boardSize);
    printBoard(board, boardSize);

}

I'm a beginner at C++, and I dont have a firm grasp on pointers, or even header files. I tried passing in the 2D array without any pointers, but the compiler gave me an error:

invalid conversion from 'const char*' to 'char'

So i tried putting in the pointers as listed above, and I get the same error

What do I do? can anyone go through my code and tell me exactly what's wrong?

Don't include .cpp files in other .cpp files until you have a very, very solid understanding of header files. That's an advanced technique that will only get you into trouble for now. — David Schwartz
– David Schwartz, Commented Mar 8, 2014 at 17:49
Can you paste the exact error you get and indicate which line you get it on? — David Schwartz
– David Schwartz, Commented Mar 8, 2014 at 17:56

David Schwartz · Accepted Answer · 2014-03-08 17:51:37Z

Your code doesn't agree with itself.

char board[10][10];

This says board is a 2D array, 10 by 10.

makeBoard(board, boardSize);

This passes board to makeBoard, which will only work if makeBoard's first parameter is compatible with a 10 by 10, 2D array.

void makeBoard(char (*myBoard)[10], int boardSize)

But this says the first parameter to makeBoard is a pointer to a 1D array. That's nothing like a 2D array -- they're completely incompatible. Arrays are compatible with pointers to their first elements. So a pointer to a 1D array has two levels of indirection -- the pointer leads you to a 1D array, which decays into a pointer to the first element. A 2D array has one level of indirection -- the array decays into a pointer to its first element.

So, which is it? Is the parameter a pointer to the contents, or a pointer to a pointer to the contents?

Why not just use std::vector instead of arrays?

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