lib.graph-families.CycleGraph.Walk.md.

Version of Sunday, January 22, 2023, 10:42 PM

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Investigations on graph-theoretical constructions in Homotopy type theory

Jonathan Prieto-Cubides j.w.w. Håkon Robbestad Gylterud

Department of Informatics

University of Bergen, Norway

{-# OPTIONS --without-K --exact-split  --allow-unsolved-metas #-}

module lib.graph-families.CycleGraph.Walk
  where
  open import foundations.Core
  open import lib.graph-definitions.Graph
  open Graph

  module
    _
    ( : Level)
    where
    open import foundations.Nat 
    open import foundations.Fin 

    open import lib.graph-families.CycleGraph 
    open import lib.graph-embeddings.Map
    open import lib.graph-transformations.U
    open import lib.graph-families.CycleGraph.Map

    open import lib.graph-families.CycleGraph.isCyclicGraph
    open import lib.graph-classes.CyclicGraph.Walk
    open import lib.graph-walks.Walk
    open import lib.graph-walks.Walk.QuasiSimple

    module
      _ (n : )
      where

      -- Between two points in U(Cn), we always have two simple walks CW- and CCW-.
      ccw
        : (a b : Node (Cycle n))
        ------------------------
         Walk (U (Cycle n)) a b

      ccw = ccw-walk (Cycle n) (Cn-is-cyclic-graph  n)
        where open UndirectedWalks

      cw
        : (a b : Node (Cycle n))
        ------------------------
         Walk (U (Cycle n)) a b

      cw = cw-walk (Cycle n) (Cn-is-cyclic-graph  n)
        where open UndirectedWalks
        -- open  lib.graph-walks.Walk.QuasiSimple.simplewalks
        -- cw-is-simple
          -- : (n : ℕ)
          -- → (x y : Node (Cycle n))
          -- → (cw n x y) is-quasi-simple
        -- cw-is-simple = {!!}

        -- cw-is-simple zero (x , <0) _ = ⊥-elim {ℓ} (n<0 {ℓ}{n = x} <0)
        -- cw-is-simple (succ n) x y = {!cw-is-simple n !}

--         ccw-is-simple
--           : (n : ℕ)
--           → (x y : Node (Cycle n))
--           → (ccw n x y) is-quasi-simple
--       {-
--       f
--         : (n : ℕ)
--         → (x y : Node (Cycle n))
--         → ((x ≡ y) × 𝟛 ℓ) + ((x ≠ y) × 𝟚 ℓ)
--         → ∑[ w ∶ Walk (U (Cycle n)) x y ] (w is-quasi-simple)

--       f n x .x (inl (idp , 𝟘₃)) = (⟨ x ⟩ , one-point-walk-is-simple {G = U (Cycle n)} x)
--       f n x .x (inl (idp , 𝟙₃)) = (ccw n x x , ccw-is-simple n x x)
--       f n x .x (inl (idp , 𝟚₃)) = (cw  n x x , cw-is-simple  n x x)
--       f n x  y (inr (x≠y , 𝟘₂)) = (ccw n x y , ccw-is-simple n x y)
--       f n x  y (inr (x≠y , 𝟙₂)) = (cw  n x y , cw-is-simple  n x y)

--       -}
--       {-
--       g
--         : (n : ℕ)
--         → (x y : Node (Cycle n))
--         → (w : Walk (U (Cycle n)) x y)
--         → w is-quasi-simple
--         → (x ≡ y) + ((w ≡ ccw n x y) + (w ≡ cw n x y))

--       g zero (zero , ()) y w w-is-simple
--       g zero (succ π₃ , ()) y w w-is-simple
--       g (succ zero) (zero , ∗) (zero , ∗) ⟨ .(0 , ∗) ⟩ w-is-simple = inl idp
--       g (succ zero) (zero , ∗) (zero , ∗) (inl x ⊙ w) w-is-simple = {!!}
--       -- = inr (inl {!!})
--       g (succ zero) (zero , ∗) (zero , ∗) (inr x ⊙ w) w-is-simple = inr (inr {!idp!})
--       g (succ zero) (zero , _) (succ zero , ()) w w-is-simple
--       g (succ zero) (zero , _) (succ (succ _) , ()) w w-is-simple
--       g (succ zero) (succ zero , ()) (zero , π₆) w w-is-simple
--       g (succ zero) (succ (succ _) , ()) (zero , π₆) w w-is-simple
--       g (succ zero) (succ zero , ()) (succ π₅ , π₆) w w-is-simple
--       g (succ zero) (succ (succ _) , ()) (succ π₅ , π₆) w w-is-simple
--       g (succ (succ n)) x y w w-is-simple = {!!}
--       -}

--       {-
--       f-is-equiv
--           : (n : ℕ)(x y : Node (Cycle n))
--           → (f n x y) is-equiv

--       f-is-equiv zero (zero , ()) _
--       f-is-equiv zero (succ _ , ()) _
--       -- ≡ 1
--       f-is-equiv (succ zero) x@(zero , ∗) (zero , ∗)
--        = λ { (⟨ .(0 , ∗) ⟩ , w-is-simple)
--                → ( -- center of the contraction
--                ((inl (idp , 𝟘₃) , pair= (idp , being-simple-is-prop {G = U (Cycle _)} (⟨ x ⟩) _ _)))
--                  -- proof it's indeed a center the above term.
--                  , λ { (inl (idp , 𝟘₃) , idp) → pair= (idp ,
--                    {!!}
--                  )
--                ; (inl (idp , 𝟙₃) , π₄) → {!π₄!}
--                ; (inl (idp , 𝟚₃) , π₄) → {!!}
--                ; (inr (x≠x , π₅) , π₄) → ⊥-elim (x≠x idp)})
--         ; ((x ⊙ p) , q) → {!!}}
--       f-is-equiv (succ zero) (zero , _) (succ zero , ())
--       f-is-equiv (succ zero) (zero , _) (succ (succ _) , ())
--       f-is-equiv (succ zero) (succ zero , ()) (zero , ∗)
--       f-is-equiv (succ zero) (succ (succ _) , ()) (zero , _)
--       -- ≡ 2
--       f-is-equiv (succ (succ zero)) (π₃ , π₄) (π₅ , π₆) = {!!}
--       -- >= 3
--       f-is-equiv (succ (succ (succ n))) x y = {!!}
--       -}


--       {-
--       Cn-walk-equiv
--         : (n : ℕ) → (x y : Node (Cycle n))
--         → ((x ≡ y) × 𝟛 ℓ) + ((x ≠ y) × 𝟚 ℓ)
--         ≃ (∑[ w ∶ Walk (U (Cycle n)) x y ] (w is-quasi-simple))
--       Cn-walk-equiv n x y = (f n x y , f-is-equiv n x y)
--       -}




--       -- open import lib.graph-classes.Planar

-- ```

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