Core degeneracy infrastructure from the LICS 2022 paper:
- Simple degeneracy detection: Checks that the singular map is injective
(composition of face maps) and all slice maps are identities.
- Parallel degeneracy detection: Checks that the singular map is the
identity (no cones in RewriteN) and all slice maps are degeneracies.
- Degeneracy detection: Combines simple and parallel checks.
- Factorisation (Lemma 7): Every degeneracy factors uniquely as
N --simple--> P --parallel--> T.
- Pullback computation (Proposition 13): Given degeneracies f: X -> T
and g: Y -> T, computes the pullback by intersecting images in Delta+.
- Helper functions: simple_degeneracy_at(), extract_singular_map(), etc.
All 53 tests pass.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Initial structure implementing the zigzag construction for associative
n-categories (LICS 2022 paper). Includes:
- monotone.rs: MonotoneMap with Wraith's R equivalence (complete)
- zigzag.rs: Zigzag<T>, ZigzagMap<S> with composition
- diagram.rs: Diagram, DiagramN, Cospan, Rewrite, Cone types
- signature.rs: Generator, Signature (complete)
- degeneracy.rs: Degeneracy detection stubs
- normalise.rs: Construction 17 algorithm structure
- typecheck.rs: Type checking against signatures
- explosion.rs: k-points and Poset for layout
- layout.rs: SpringConstraint API surface
All 33 unit tests pass.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
