PL segment models for polygonal arcs #
theorem
LeanEval.Topology.ClassificationOfSurfaces.Moise.BrokenLineData.exists_PL_segment_model
{U : Set Plane}
(B : BrokenLineData U)
:
∃ (S : PlaneComplex) (F : Plane → Plane),
S.support = segment ℝ (planePoint 0 0) (planePoint (↑B.resolvedWalk.length) 0) ∧ IsPLOn S F ∧ (∀ s ∈ S.simplexes, s.card ≤ 2) ∧ Set.InjOn F S.support ∧ F '' S.support = B.resolvedCarrier ∧ F (planePoint 0 0) = B.start ∧ F (planePoint (↑B.resolvedWalk.length) 0) = B.finish
A polygonal arc extracted from a broken line is the endpoint-preserving PL image of a straight segment.