42e98bd3c9
This PR changes the signature of `Array.swap`, so it takes `Nat` arguments with tactic provided bounds checking. It also renames `Array.swap!` to `Array.swapIfInBounds`.
20 lines
725 B
Text
20 lines
725 B
Text
def Array.swaps (a : Array α) : List (Fin a.size × Fin a.size) → Array α
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| [] => a
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| (i, j) :: ijs =>
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have : (a.swap i j).size = a.size := a.size_swap _ _
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swaps (a.swap i j) (ijs.map (fun p => ⟨⟨p.1.1, by simp⟩, ⟨p.2.1, by simp⟩⟩))
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termination_by l => l.length
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set_option maxHeartbeats 1000 in
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theorem Array.swaps_cancel (a : Array α) (l : List (Fin a.size × Fin a.size)) : a.swaps (l ++ l.reverse) = a :=
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match l with
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| [] => sorry
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| c :: cs =>
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have h : a.size = (a.swaps [c]).size := sorry
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have ih1 : ((a.swaps [c]).swaps ((h ▸ cs) ++ (h ▸ cs).reverse)) = (a.swaps [c]) :=
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swaps_cancel (a.swaps [c]) (h ▸ cs)
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sorry
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termination_by l.length
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decreasing_by sorry
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