c039e29a3f
This PR cuts some edges from the import graph. Specifically: - `TreeMap` and `HashMap` no longer depend on `String`, so now the expensive things are all in parallel instead of partially in sequence - `Omega` no longer relies on `List` lemmas - The section of the import graph between `Init.Omega` and `Init.Data.Bitvec.Lemmas` is cleaned up a bit
30 lines
891 B
Text
30 lines
891 B
Text
/-
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Copyright (c) 2016 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Leonardo de Moura
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-/
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module
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prelude
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public import Init.Core
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public section
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/--
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The `BEq α` and `Hashable α` instances on `α` are compatible. This means that that `a == b` implies
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`hash a = hash b`.
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This is automatic if the `BEq` instance is lawful.
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-/
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class LawfulHashable (α : Type u) [BEq α] [Hashable α] where
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/-- If `a == b`, then `hash a = hash b`. -/
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hash_eq (a b : α) : a == b → hash a = hash b
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/--
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A lawful hash function respects its Boolean equality test.
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-/
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theorem hash_eq [BEq α] [Hashable α] [LawfulHashable α] {a b : α} : a == b → hash a = hash b :=
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LawfulHashable.hash_eq a b
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instance (priority := low) [BEq α] [Hashable α] [LawfulBEq α] : LawfulHashable α where
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hash_eq _ _ h := eq_of_beq h ▸ rfl
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