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trunk endpoint from cf

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Freiman.trunk_endpoint_from_cf

by tp · Sep 9, 2026 · Mathlib 0df444a (Lean v4.33.1)

algebracontinued-fractionsformalization

The strict second width branch, virtual mixed endpoint and optional7/5 shortening enumerate the actual endpoint; common odd parity changes both the sign and endpoint flag. All rational tails are interpreted by the shared exact CF evaluation.

Preamble
import Definitions.Def_Freiman_trunkGeometry
import Mathlib.Tactic.FinCases
import Mathlib.Tactic.Linarith

open Freiman
Formal statement
theorem Freiman.trunk_endpoint_from_cf (hc : ∀ (w : List ℕ+) (z : CertField), 0 ≤ certFieldVal z → certFieldVal (lowerHistoryCF w z) = prefixEval w (certFieldVal z)) :
    TrunkEndpointLaw := by
  sorry
Source
Report Proposition4.1 s15:trunk, printed report p28; original source pp120–126. Complete sixteen-state trunk certificate,58230 records,90 case plans, with three explicitly unfilled interfaces.

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