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-(* tripla dipendente, suggerimento \SHcy *)
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-inductive bisigma (A,B:Type) (P:A → B → Type) : Type ≝
- bisigma_intro: ∀x:A.∀y:B.P x y → bisigma A B P.
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-definition bisigmaFst ≝
-λT1,T2:Type.λf:T1 → T2 → Type.λs:bisigma T1 T2 f.match s with [ bisigma_intro x _ _ ⇒ x ].
-definition bisigmaSnd ≝
-λT1,T2:Type.λf:T1 → T2 → Type.λs:bisigma T1 T2 f.match s with [ bisigma_intro _ x _ ⇒ x ].
-definition bisigmaThd ≝
-λT1,T2:Type.λf:T1 → T2 → Type.λs:bisigma T1 T2 f.match s return λs.f (bisigmaFst ??? s) (bisigmaSnd ??? s) with [ bisigma_intro _ _ x ⇒ x ].