49 lines
2 KiB
Text
49 lines
2 KiB
Text
/-
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Copyright (c) 2018 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, Mario Carneiro, Markus Himmel
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-/
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prelude
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import Std.Data.DHashMap.Internal.AssocList.Basic
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/-!
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# Definition of `DHashMap.Raw`
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This file defines the type `Std.Data.DHashMap.Raw`. All of its functions are defined in the module
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`Std.Data.DHashMap.Basic`.
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-/
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set_option linter.missingDocs true
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set_option autoImplicit false
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universe u v
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namespace Std.DHashMap
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/--
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Dependent hash maps without a bundled well-formedness invariant, suitable for use in nested
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inductive types. The well-formedness invariant is called `Raw.WF`. When in doubt, prefer `DHashMap`
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over `DHashMap.Raw`. Lemmas about the operations on `Std.Data.DHashMap.Raw` are available in the
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module `Std.Data.DHashMap.RawLemmas`.
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The hash table is backed by an `Array`. Users should make sure that the hash map is used linearly to
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avoid expensive copies.
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This is a simple separate-chaining hash table. The data of the hash map consists of a cached size
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and an array of buckets, where each bucket is a linked list of key-value pais. The number of buckets
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is always a power of two. The hash map doubles its size upon inserting an element such that the
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number of elements is more than 75% of the number of buckets.
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The hash map uses `==` (provided by the `BEq` typeclass) to compare keys and `hash` (provided by
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the `Hashable` typeclass) to hash them. To ensure that the operations behave as expected, `==`
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should be an equivalence relation and `a == b` should imply `hash a = hash b` (see also the
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`EquivBEq` and `LawfulHashable` typeclasses). Both of these conditions are automatic if the BEq
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instance is lawful, i.e., if `a == b` implies `a = b`.
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-/
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structure Raw (α : Type u) (β : α → Type v) where
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/-- The number of mappings present in the hash map -/
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size : Nat
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/-- Internal implementation detail of the hash map -/
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buckets : Array (DHashMap.Internal.AssocList α β)
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end Std.DHashMap
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