Does anyone know how this library maintains geometric robustness in the face of rounding errors? E.g. if you rotate a unit square by 45 degrees (giving irrational coordinates), then rotate it back and subtract it from the original, you are left with exactly nothing?
Exactness is not "advertized" on the main page or as a "design principle" but it is there !
Geogram uses "arithmetic expansions", arrays of floating point numbers that can represent numbers with arbitrary precision while being reasonably performant (it is the same thing used by Jonathan Shewchuk in his predicates). In addition, besides predicates, Geogram can use arithmetic expansions to represent intermediary results of computation (I'm currently developing boolean operations that extensively make use of this feature).
