Library Coq.Logic.ProofIrrelevanceFacts

This defines the functor that build consequences of proof-irrelevance

Require Export EqdepFacts.

Module Type ProofIrrelevance.

  Axiom proof_irrelevance : forall (P:Prop) (p1 p2:P), p1 = p2.

End ProofIrrelevance.

Module ProofIrrelevanceTheory (M:ProofIrrelevance).

Proof-irrelevance implies uniqueness of reflexivity proofs

  Module Eq_rect_eq.
    Lemma eq_rect_eq :
      forall (U:Type) (p:U) (Q:U -> Type) (x:Q p) (h:p = p),
        x = eq_rect p Q x p h.
  End Eq_rect_eq.

Export the theory of injective dependent elimination

  Module EqdepTheory := EqdepTheory(Eq_rect_eq).
  Export EqdepTheory.

  Scheme eq_indd := Induction for eq Sort Prop.

We derive the irrelevance of the membership property for subsets

  Lemma subset_eq_compat :
    forall (U:Type) (P:U->Prop) (x y:U) (p:P x) (q:P y),
      x = y -> exist P x p = exist P y q.

  Lemma subsetT_eq_compat :
    forall (U:Type) (P:U->Prop) (x y:U) (p:P x) (q:P y),
      x = y -> existT P x p = existT P y q.

End ProofIrrelevanceTheory.