module A201607.OlderBasicILP.Indirect where

open import A201607.Common.Context public


-- Propositions of intuitionistic logic of proofs, without ∨, ⊥, or +.

infixr 10 _⦂_
infixl 9 _∧_
infixr 7 _▻_
data Ty (X : Set) : Set where
  α_  : Atom → Ty X
  _▻_ : Ty X → Ty X → Ty X
  _⦂_ : X → Ty X → Ty X
  _∧_ : Ty X → Ty X → Ty X
  ⊤  : Ty X

module _ {X : Set} where
  infix 7 _▻◅_
  _▻◅_ : Ty X → Ty X → Ty X
  A ▻◅ B = (A ▻ B) ∧ (B ▻ A)


  -- Additional useful propositions.

  _⦂⋆_ : ∀ {n} → VCx X n → VCx (Ty X) n → Cx (Ty X)
  ∅        ⦂⋆ ∅       = ∅
  (TS , T) ⦂⋆ (Ξ , A) = (TS ⦂⋆ Ξ) , (T ⦂ A)