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A function from Not (x = y) to decEq x y = No _ was added.

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Denis Buzdalov 2021-02-16 13:47:28 +03:00 committed by G. Allais
parent f390fba766
commit 0ac34538ec
1 changed files with 7 additions and 0 deletions
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7
libs/base/Decidable/Equality/Core.idr
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@ -27,3 +27,10 @@ decEqSelfIsYes : DecEq a => {x : a} -> decEq x x = Yes Refl
decEqSelfIsYes {x} with (decEq x x)
decEqSelfIsYes {x} | Yes Refl = Refl
decEqSelfIsYes {x} | No contra = absurd $ contra Refl
||| If you have a proof of inequality, you're sure that `decEq` would give a `No`.
export
decEqContraIsNo : DecEq a => {x, y : a} -> Not (x = y) -> (p ** decEq x y = No p)
decEqContraIsNo uxy with (decEq x y)
decEqContraIsNo uxy | Yes xy = absurd $ uxy xy
decEqContraIsNo _ | No uxy = (uxy ** Refl)