17 lines
517 B
Text
17 lines
517 B
Text
/-
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Copyright (c) 2024 Lean FRO, LLC. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Markus Himmel
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-/
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prelude
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import Init.Data.Array.Lemmas
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import Init.Data.List.Nat.TakeDrop
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namespace Array
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theorem exists_of_uset (self : Array α) (i d h) :
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∃ l₁ l₂, self.data = l₁ ++ self[i] :: l₂ ∧ List.length l₁ = i.toNat ∧
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(self.uset i d h).data = l₁ ++ d :: l₂ := by
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simpa [Array.getElem_eq_data_getElem] using List.exists_of_set _
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end Array
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