Based on the rest of the original paragraph, I understand he refers to the fact that you have to choose either one when desigining a library, and then you're st

Based on the rest of the original paragraph, I understand he refers to the fact that you have to choose either one when desigining a library, and then you're stuck with it (and its various consequences) in your API for better or worse -- and your library users are stuck with it too. In other words: if you design a polygon clipping library, do you design your API so that users would write `polygon1.clip(polygon2)`, or `clipper::clip(polygon1, polygon2)`? edit: also, from reading further down, I understand the discussed issue is that after you define the API as `polygon1.clip(polygon2)`, you can't easily use the 'clip' method in places where a f(a,b) would be required, although it's effectively equivalent. And it's impossible the other way round too.