constructor
α : Type u
inst✝ : DecidableEq α
a : α
as : Array α
⊢ (∃ x, (∃ n, List.get as.data n = x) ∧ decide (a = x) = true) ↔ ∃ n, List.get as.data n = a
case mp
α : Type u
inst✝ : DecidableEq α
a : α
as : Array α
⊢ (∃ x, (∃ n, List.get as.data n = x) ∧ decide (a = x) = true) → ∃ n, List.get as.data n = a

case mpr
α : Type u
inst✝ : DecidableEq α
a : α
as : Array α
⊢ (∃ n, List.get as.data n = a) → ∃ x, (∃ n, List.get as.data n = x) ∧ decide (a = x) = true