In-Reply-To: <cpsv4p$foa$1@sea.gmane.org> michaeltoksvig@yahoo.com (michael toksvig) wrote (abridged):
you might consider adding operator[] to point and size
also, consider defining area in terms of 2 points, and adding operator[] to that, too
I was about to say the same thing :-) I'd go further, and expose the array. class box { point data_[2]; public: point *data() { return data_; } static size_t size() { return 2; } point &operator[]( size_t i ) { assert(i < 2); return data_[i]; } // Maybe begin/end too. const point &top_left() { return data_[0]; } const point &bottom_right() { return data_[1]; } float top() { return data_[0][1]; } float left() { return data_[0][0]; } float bottom() { return data_[1][1]; } float right() { return data_[1][0]; } size extent() const { return bottom_right() - top_left(); } float width() const { return right() - left(); } float height() const { return bottom() - top(); } point centre() const { return top_right() + extent()/2; } // ... void set_top_left( const point &p ); void set_top( float f ); void set_centre( const point &p ); // ... }; This is because you will almost certainly want transforms that act on arrays of points, and it will sometimes be convenient if they can act on rectangles too. I would provide get/set methods which are independent of representation. I'd consider allowing things like ++box.top() too. Currently I think the convenience is not worth the loss of purity. ++box[0][1] should work, though. On naming... I think "area" is the wrong name. To me an area can be any shape, or alternatively, every shape has an area. I would expect circle.area() to return pi*r*r. "Rectangle" is better, but what we actually have here is a special kind of rectangle which is aligned with the axis. A rotated rectangle needs more than 2 points. So conceptually we need two rectangle types. I suggest "rectangle" is reserved for the general case, and the aligned one is called "box". As in "bounding box". It has the benefit of being short. I see no benefit in using "position" instead of the usual "point". "Point" is shorter. It's hard to improve on "size" :-) I would seriously consider replacing float with a typedef, perhaps with another typedef for distances and offsets. Even without type checking, I think using more exact type names helps to clarify thought. [Later...] I've looked at the code in the zip file now. I see it doesn't match the email. It uses a different representation and adds several member functions, although not as many as me. I am surprised to see things like size*size and size/size. I see the design is being driven by the needs of a windowing system, when I am being driven by the needs of a graphics/drawing system. That has led to different results, which I suspect is a bad thing. At any rate, it has convinced me that exposing raw member variables (like area.pos) is a mistake. -- Dave Harris, Nottingham, UK