Thread: multidimensional array as a function argument

hello!
I am trying to call a function that has multi dimensional array as one of its arguments. My Dev C++ gives me crap with this code:

Code:

#include <iostream>
using namespace std;

void printarray( int arr[] [3] [3],int verlen = 3,int horlen = 3);
int main(void)
{
int x[3][3];
for (int b(0);b<4;b++){
    for(int c(0); c<4; c++){
                 x[c][b] = c;
                 
                 }           
                 }
printarray(x,3,3);
cin.get();
}

void printarray( int arr [3] [3],int verlen = 3,int horlen = 3){
     for(int x(0);x<=verlen; x++){
        for(int y(0); y<=horlen;y++){
                cout<< arr[x][y];
                }
        cout<<"\n";
        }
        }

Dev C++ has this to say about my code:

In function `int main()':
cannot convert `int (*)[3]' to `int (*)[3][3]' for argument `1' to `void printarray(int (*)[3][3], int, int)'
[main.o] Error 1

What am i doing wrong?

The first problem is that your printarray function declaration (prototype) and function definition do not match. The next problem is that since your function declaration declares default arguments, your function definition should omit them instead of declaring them again.

Oh, and your indentation can be improved.

EDIT:
Looking more closely at the code, you have another problem: you are accessing the array out of bounds. For example, you access x[3][3] both in main() and in printarray().

Originally Posted by laserlight

Oh, and your indentation can be improved.

This is Dev-C++'s fault.
It create this poor, bad indentation by default if you don't intervene.
I'd say switch IDE.
A list of free ones: http://cpwiki.sf.net/IDE

ok I guess the tutorial i am reading is shady,

it says that:

Code:

void procedure (int myarray[][3][4])

is a valid function prototype
but when I try

Code:

void printarray( int arr[] [4] [4],int verlen = 3,int horlen = 3);
int x[4][4];
int main(void)
{
for (int b(0);b<5;b++){
   for(int c(0); c<5; c++){
                            x[c][b] = c;                
                          }                  
                      }
printarray(x,4,4);
cin.get();
}

void printarray( int arr[] [4] [4],int verlen,int horlen){
     for(int x(0);x<=verlen; x++){
        for(int y(0); y<=horlen;y++){
                cout<< arr[x][y];
                }
        cout<<"\n";
        }
        }

it gives me an error but...

Code:

void printarray( int arr [4] [4],int verlen = 3,int horlen = 3);
int x[4][4];
int main(void)
{
for (int b(0);b<5;b++){
   for(int c(0); c<5; c++){
                            x[c][b] = c;                
                          }                  
                      }
printarray(x,4,4);
cin.get();
}

void printarray( int arr [4] [4],int verlen,int horlen){
     for(int x(0);x<=verlen; x++){
        for(int y(0); y<=horlen;y++){
                cout<< arr[x][y];
                }
        cout<<"\n";
        }
        }

is fine...

Of course it is. The number of [ and ] tells the compiler how many dimensions the array you're passing is supposed to have.
And in the first example, you tell the compiler it has 3, while you pass an array that has 2.

Also,
int main(void)
can be written as
int main()
(same thing, no need for void.)

And the variable x should be local rather than global.

> ok I guess the tutorial i am reading is shady
Or flat out wrong. Post a link to it.

> is a valid function prototype
It is, if you were passing a 3D array to it, and not a 2D array.

Copy/paste always works, and saves a hell of a lot of thinking.
If you have
int a[X][Y];

Then the prototype for a function would be
void foo ( int a[X][Y] );
The occasional tool will complain about the first dimension not being empty, but that's easily fixed to become [ ][Y]

And the call would be
foo( a );