manipulating multidimensional arrays with functions in C++

Question

I am trying to modify the contents of a 2D array in C++ using a function. I haven\'t been able to find information on how to pass a 2D array to a function by reference and

Answer 1

C++ allows you to encapsulate code structures like this into an object, for example an array has the std::vector and std::array object.

I personally roll my own matrix containers. This way you don't have to worry about the details of how they are passed.

A basic example of a matrix implemenation could be:

template
class matrix
{
public:                     //TYPEDEFS
    typedef                         T                                                       value_type;
private:
    typedef                 std::vector         vect_type;
public:
    typedef typename        vect_type::iterator             iterator;
    typedef typename        vect_type::const_iterator       const_iterator;

private:            //DATAMEMBERS
    vect_type values;
    size_t x_sz, y_sz;/not const for assingment reasons

public:                     //MEMBER FUNCTIONS
    matrix(const matrix&)           =default;
    matrix(matrix&&)                =default;
    matrix& operator=(const matrix&)=default;
    matrix& operator=(matrix&&)     =default;

    matrix(size_t x_sz_=0u, size_t y_sz_=0u, value_type t=value_type())
    : values(x_sz_*y_sz_, t)
    , x_sz(x_sz_)
    , y_sz(y_sz_)
    { }

    //return        symbol          const   body
    size_t          x_size()        const   { return x_sz; }
    size_t          y_size()        const   { return y_sz; }

    iterator        begin()                 { return values.begin();        }
    iterator        end()                   { return values.end();          }
    const_iterator  begin()         const   { return values.cbegin();       }
    const_iterator  end()           const   { return values.cend();         }
    const_iterator  cbegin()        const   { return values.cbegin();       }
    const_iterator  cend()          const   { return values.cend();         }

    value_type& at(size_t x, size_t y)
    {
            return values.at(y*x_sz+x);
    }

    const value_type& at(size_t x, size_t y) const
    {
            return values.at(y*x_sz+x);
    }
};  //class matrix

Then you simply do the following:

 void func(const mat& m)....
 :::

 matrix mat(3,3);

 //this isn't necessary as the ctor take a default value,
 // however it show you how you might iterate through the values.
 for(size_t y=0; y!=mat.y_size(); ++y)
    for(size_t x=0; x!=mat.x_size(); ++x)
        mat.at(x, y)=0; 

func(mat); //as param