Passing a 2d array to a method

Question

const int width = 100, height = 100;
void clearBoard(bool *board[]);

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

    bool gameboard[width][height];
    clearBoard(gameboard);

    QApplication a(argc, argv);
    MainWindow window;
    window.show();

    return a.exec();
}

void clearBoard(bool *board[]){
       for(int x = 0; x < width; x++)
        for(int y = 0; y < height; y++)
            board[x][y] = false;
}

The error at hand is:

C2664: 'void clearBoard(bool *[])' : cannot convert argument 1 from 'bool [100][100]' to 'bool *[]'

I think I have the basic understanding of how pointers work, and 2D pointer, but for some reason this won't work. Would love it if someone could explain what I'm getting wrong.

you should have `bool board[][100]` in the function parameter... — Irrational Person, Feb 24 '15 at 18:29
Possible duplicate: http://stackoverflow.com/questions/8767166/passing-2d-array-to-function — Thomas Matthews, Feb 24 '15 at 18:33
When arrays decay to pointer, it always decays to 1d pointer `T*` no matter it is a 1d array or 2d. To pass it to the function, use `T[][N]` or `&T[M][N]` (which is more idiomatic in C++). If you insist on passing as pointer, you need to calculate the offset yourself. — SwiftMango, Feb 24 '15 at 18:34

hamid attar · Accepted Answer · 2015-02-24T18:40:03.677

1

When passing an n-dimensional array as a function argument, you can let only the first dimension be implicit. Please try:

void clearBoard(bool board[][height]){
       for(int x = 0; x < width; x++)
        for(int y = 0; y < height; y++)
            board[x][y] = false;
}

edited Feb 24 '15 at 18:40

answered Feb 24 '15 at 18:34

hamid attar

388
1
8

you should mention the other methods too like pointer to pointer method or array of pointers methods. – Irrational Person Feb 24 '15 at 18:35

Passing a 2d array to a method

1 Answers1