The first part seems the wrong way to do it (treating it as an example). You would presumably overload area() on the object type, not on individual parameters representing the object's geometry. 'circle.area(r)' is even weirder - extracting radius just doesn't make sense here.

<SomeGeometricObject>.area() is right AFAICS.

Which I think is what you're getting at anyway.

But IMO overloading used right is cleaner than not having overloading.