Hi Pierre,
[...] and that something simplier could even work : instead of a variant, a tuple of back_inserter could do the trick very nicely.
vector<point2D> myPoints; vector<line2D> myLines; vector<polygon2D> myPolygons;
typedef tuple<vector<point2D>, vector<line2D>, vector<polygon2D> > AFakeTupleType;
intersection_inserter<AFakeTupleType>(poly1, poly2, make_tuple(back_inserter(myPoints), back_inserter(myLines), back_inserter(myPolygons));
Please note there is no object of type AFakeTupleType constructed. This type is just used to drive the algorithm.
The output can be dispatched to different vectors, and the input is still 1 object. Then, the user can simply check the lenght of each result to check if there was an intersection.
This is less mathematics oriented, but still completely usable, and more simplier, because of the redirection of the result to the selected vectors.
You already use tuple, so maybe references wrapper in AFakeTupleType would be needed to make the distinction with your other tuple.
What do you think of that? Do you see any drawbacks?
I think it will work. It would certainly solve the performance issue, you get all three collections back in one calculation. Potential drawbacks (or, better stated, issues): - it is more complex; I think (personally) that most users want only the intersected polygon back. To always require the complexity described here might be a bit too much - but that is no real problem, because we can create another function for it, or even automatically detecting what is happening here, in the tag dispatching - the AFakeTupleType (tuple of vectors) does not match the make_tuple (tuple of output iterators), as you said - but also that is no real issue (actually, it is the same as it is working now, the OutputType and the output iterator) I think it is feasable and a very good idea; but not by default (because of the complexity involved, also for the library user). But if people want to get all these three different things back, yes, I think this is the best option discussed until now. Does the trick very nicely, as you said, indeed. Thanks! Regards, Barend