Passing a struct with multiple entries in c++

Question

I am trying to pass a coordinate, which is defined as struct with 2 integer parameters (the struct is called coord) the following way:

UpdateB({0,0}); 

where the input argument is of type coord (i.e. in the above statement I am trying to pass a coordinate 0,0). UpdateB is some function. I am getting an error, any ideas what the problem could be?

Answer 1

Make a constructor accepting two argumnets. Pass it as follows:

MyFunc(Point2d(0,0));

Answer 2

Pavel's got it spot on. If you want to create the struct instance as you're passing it to the function, you'll need to make a constructor for it. Then create a new instance of coord as the argument you're passing to the function. For the struct, something like...

struct coord
{
    int x, y;

    coord(int xvalue, int yvalue)
    {
        x = xvalue;
        y = yvalue;
    }
};

...should do the trick. Then just run...

UpdateB(coord(x, y));

...where x and y are your values.

Answer 3

The syntax you are using would be valid C++0x (uniform initializers) and valid C99 (compound literals).
In C++03 you have to use either user-defined constructors or helper functions, the curly-brace syntax only works for aggregate initialization.

If your struct is a POD and you need it to stay one, you have to use a helper function:

coord make_coord(int x, int y) {
    coord c = {x, y};
    return c;
}

UpdateB(make_coord(x, y));

Otherwise, as already mentioned, give it a constructor

Answer 4

Pavel Radzivilovsky's solution is right (+1).

However you have to know that the coming new standart C++0x will allow the syntax of your example if you provide a constructor with two parameters (and maybe if you provide a constructor with initializer list but that's not useful here).

This feature is already available in GCC starting v4.4, if you use it you can enable it by enabling C++0x.