C++: Pass two-dimensional array to function - c++

Question

This is probably so simple, but I can't figure out why this won't compile.
void display(int);
const int rows = 2;
const int cols = 2;
int main()
{
int ray[rows][cols] = {{1,2 },
{3,4}};
display(ray);
return 0;
}
void display(const int ray[][cols]){
for(int i = 0; i < 2; i ++){
for(int j = 0; j < 2; j ++){
cout << ray[i][j] << endl;
}
}
}
invalid conversion from ‘int (*)[2]’ to ‘int’ [-fpermissive]|

Answer 1

This code will work
const int rows = 2;
const int cols = 2;
void display( const int ray[][cols]);
int main()
{
int ray[rows][cols] = {{1,2 },
{3,4}};
display(ray);
return 0;
}
void display( const int ray[][cols]){
for(int i = 0; i < 2; i ++){
for(int j = 0; j < 2; j ++){
cout << ray[i][j] << endl;
}
}
}
Your function definition and function declaration do not match, one of them is of type int while the other is type void
Your function declaration is
void display(int);
and the definition is
int display(const int ray[0][cols])
and
int display(const int ray[0][cols])
^
0 ?

Answer 2

I think I see the problem here
The prototype is wrong. If you want a 2D array arg, it's more like this
int display(const int ray**);

Answer 3

The forward declaration of display is wrong. Either fix forward declaration or change order of functions:
#include <iostream>
using namespace std;
const int rows = 2;
const int cols = 2;
int display(const int ray[0][cols]){
for(int i = 0; i < 2; i ++){
for(int j = 0; j < 2; j ++){
cout << ray[i][j] << endl;
}
}
}
int main()
{
int ray[rows][cols] = {{1,2 },
{3,4}};
display(ray);
return 0;
}
Live Example

Answer 4

Since you use global variables anyway, the easy thing is to change your declaration of display:
Declare display like this:
void display(int** array)
{...}
In this case you will actually be able to send your 2D array to the function because the type will match. A 2D array is an array of arrays and an array is just a pointer associated with some memory.

Answer 5

I am not giving the appropriate answer to this question. But an alternative.
As C++ suggests to use std::string inplace of char* . It also suggests to use vectors instead of array wherever applicable.
#include <iostream>
#include <vector>
void display( std::vector<std::vector<int>> );
int main()
{
std::vector<std::vector<int>> int_vec{ { 1 , 2 } , { 3 , 4 } };
display( int_vec );
system("PAUSE");
return EXIT_SUCCESS;
}
void display( std::vector<std::vector<int>> integer_vector )
{
for( auto& i : integer_vector )
{
for( auto& j : i )
{
std::cout << j << std::endl;
}
}
}
The global variables as rows and cols are gone :).