source: src/utilities/sigma.ma @ 1285

Last change on this file since 1285 was 1266, checked in by sacerdot, 9 years ago

Added second projection.

File size: 376 bytes
Line 
1include "basics/types.ma".
2
3(* Stuff about Sigma types *)
4definition pi1: ∀A.∀P:A → Prop. (Σx:A. P x) → A ≝
5 λA,P,c. match c with [ dp w _ ⇒ w ].
6coercion pi1: ∀A.∀P:A → Prop.∀p:(Σx:A. P x).A ≝ pi1 on _p:Σx:?.? to ?.
7
8definition pi2: ∀A.∀P:A → Prop. ∀x:Σx:A. P x. P x ≝
9 λA,P,c. match c return λx:Σx:A. P x. P x with [ dp _ p ⇒ p ].
10
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