Booleans, decomposition, area, simplicity, hull, bounds, mitred offset
and vertex cleaning. Booleans go to GEOS, which is the reason Shapely was
chosen. The decomposition does not.
BOSL2 region_parts counts by nesting parity, not connectivity: a path
takes a level from how many others contain the midpoint of its first
edge, even levels are outer boundaries, their odd children are holes.
SECTION_PARTS == 1 is an exact assertion, and Shapely agreeing with that
count is a coincidence that holds for well-formed input and not
otherwise, so the decomposition is transcribed and both the part count
and the area derive from it.
is_region_simple is treated as a manifold precondition rather than a
diagnostic. An outline that touches itself measures perfectly and cannot
be tessellated, so it must fail here and not at export.
Developed against Shapely 2.1.2 / GEOS 3.13.1, matching CT 100. Boolean
results on near-degenerate geometry can shift between GEOS releases; if
the oracle ever disagrees by one part after an upgrade, look there first.
39 tests, all arithmetic on rectangles. Mutation run found a real gap:
nothing distinguished on-boundary from outside in the nesting probe until
a shared-edge case was added. Eight mutations now caught.
Oracle acceptance still skips; 236 unchanged.
TheRON
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