Should a function which takes dimensions/coordinates take them as multiple parameters, or one object? [duplicate]

Question

I'm mainly thinking of x,y coordinates but I guess 3D coordinates and higher also apply.

Let's say I'm writing a function to return the center of a rectangle given its width and height. Which is the more logically correct out of

center(width, height) {
    return {
        x: width / 2,
        y: height / 2
    };
}

and

center(dimensions) {
    return {
        x: dimensions.width / 2,
        y: dimensions.height / 2
    };
}

?

I know in reality both ways would be fine... but logically, should coordinates or dimensions be thought of as one item or many?

Answer 1

It's better to bundle them into objects. That way, you only need to care about the internal structure when you want to access one of the fields. Compare this:

dimensions = someArea.calculateDimensions();
theCenter = center(dimensions.width, dimensions.height);
someObject.moveTo(theCenter.x, theCenter.y);

To this:

someObject.moveTo(center(someArea.calculateDimensions()));

The second version:

• Works in 2D and 3D.
• Doesn't care if the field names are x, y or top, left(notice the different order), width, height or w, h or whatever.
• Much simpler.

Another benefit of using objects is that you can't accidentally treat, for example, coordinates as dimensions. You have to do so explicitly. This can prevent all sort of weird logical bugs...

Answer 2

If you use vector arithmetic or vector algebra, your data type will make the conversion from mathematics to code much easier if you bundle the coordinates. Vector arithmetic or algebra uses the vector or point as a single unit.

Answer 3

If you have existing code, follow it's convention. Which may well be a mishmash, i.e. support both options.

BTW, there is often a reasonable 3rd option, if the ordering is "obvious", such as Cartesian coordinates, to pass an array of coordinates. So you could do (pseudocode)

center(dimensions) {
  float c = new float(dimensions.length);
  for (int i = 0; i < dimensions.length; i++)
    c[i] = dimensions[i] / 2;
  return c;
}