Tree sets #
This file develops the type Std.TreeSet of tree sets.
Lemmas about the operations on Std.Data.TreeSet will be available in the
module Std.Data.TreeSet.Lemmas.
See the module Std.Data.TreeSet.Raw.Basic for a variant of this type which is safe to use in
nested inductive types and Std.Data.ExtTreeSet.Basic for a variant with extensionality.
Tree sets.
A tree set stores elements of a certain type in a certain order. It depends on a comparator function that defines an ordering on the keys and provides efficient order-dependent queries, such as retrieval of the minimum or maximum.
To ensure that the operations behave as expected, the comparator function cmp should satisfy
certain laws that ensure a consistent ordering:
- If
ais less than (or equal) tob, thenbis greater than (or equal) toaand vice versa (see theOrientedCmptypeclass). - If
ais less than or equal tobandbis, in turn, less than or equal toc, thenais less than or equal toc(see theTransCmptypeclass).
Keys for which cmp a b = Ordering.eq are considered the same, i.e., there can be only one of them
be contained in a single tree set at the same time.
To avoid expensive copies, users should make sure that the tree set is used linearly.
Internally, the tree sets are represented as size-bounded trees, a type of self-balancing binary search tree with efficient order statistic lookups.
For use in proofs, the type Std.ExtTreeSet of extensional tree sets should be preferred. This
type comes with several extensionality lemmas and provides the same functions but requires a
TransCmp instance to work with.
These tree sets contain a bundled well-formedness invariant, which means that they cannot
be used in nested inductive types. For these use cases, Std.TreeSet.Raw and
Std.TreeSet.Raw.WF unbundle the invariant from the tree set. When in doubt, prefer
TreeSet over TreeSet.Raw.
Internal implementation detail of the tree map.
Instances For
Creates a new empty tree set. It is also possible and recommended to
use the empty collection notations ∅ and {} to create an empty tree set. simp replaces
empty with ∅.
Equations
- Std.TreeSet.empty = { inner := Std.TreeMap.empty }
Instances For
Equations
- Std.TreeSet.instEmptyCollection = { emptyCollection := Std.TreeSet.empty }
Two tree sets are equivalent in the sense of Equiv iff all the values are equal.
Equations
- Std.TreeSet.«term_~m_» = Lean.ParserDescr.trailingNode `Std.TreeSet.«term_~m_» 50 51 (Lean.ParserDescr.binary `andthen (Lean.ParserDescr.symbol " ~m ") (Lean.ParserDescr.cat `term 51))
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Inserts the given element into the set. If the tree set already contains an element that is
equal (with regard to cmp) to the given element, then the tree set is returned unchanged.
Note: this non-replacement behavior is true for TreeSet and TreeSet.Raw.
The insert function on TreeMap, DTreeMap, TreeMap.Raw and DTreeMap.Raw behaves
differently: it will overwrite an existing mapping.
Instances For
Equations
- Std.TreeSet.instInsert = { insert := fun (e : α) (s : Std.TreeSet α cmp) => s.insert e }
Checks whether an element is present in a set and inserts the element if it was not found.
If the tree set already contains an element that is equal (with regard to cmp to the given
element, then the tree set is returned unchanged.
Equivalent to (but potentially faster than) calling contains followed by insert.
Equations
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Returns true if a, or an element equal to a according to the comparator cmp, is contained
in the set. There is also a Prop-valued version of this: a ∈ t is equivalent to
t.contains a = true.
Observe that this is different behavior than for lists: for lists, ∈ uses = and contains uses
== for equality checks, while for tree sets, both use the given comparator cmp.
Instances For
Equations
- Std.TreeSet.instMembership = { mem := fun (m : Std.TreeSet α cmp) (a : α) => m.contains a = true }
Equations
Checks if given key is contained and returns the key if it is, otherwise none.
The result in the some case is guaranteed to be pointer equal to the key in the map.
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Retrieves the key from the set that matches a. Ensures that such a key exists by requiring a proof
of a ∈ m. The result is guaranteed to be pointer equal to the key in the set.
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Checks if given key is contained and returns the key if it is, otherwise panics. If no panic occurs the result is guaranteed to be pointer equal to the key in the set.
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Checks if given key is contained and returns the key if it is, otherwise fallback.
If they key is contained the result is guaranteed to be pointer equal to the key in the set.
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Tries to retrieve the smallest element that is greater than or equal to the
given element, returning none if no such element exists.
Instances For
getGE, getGT, getLE, getLT can be found in Std.Data.TreeSet.AdditionalOperations.
Tries to retrieve the smallest element that is greater than or equal to the given element, panicking if no such element exists.
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Tries to retrieve the smallest element that is greater than or equal to the
given element, returning fallback if no such element exists.
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Tries to retrieve the smallest element that is greater than the given element,
returning fallback if no such element exists.
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Tries to retrieve the largest element that is less than or equal to the
given element, returning fallback if no such element exists.
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Tries to retrieve the smallest element that is less than the given element,
returning fallback if no such element exists.
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Removes all elements from the tree set for which the given function returns false.
Equations
- Std.TreeSet.filter f m = { inner := Std.TreeMap.filter (fun (a : α) (x : Unit) => f a) m.inner }
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Monadically computes a value by folding the given function over the elements in the tree set in ascending order.
Equations
- Std.TreeSet.foldlM f init t = Std.TreeMap.foldlM (fun (c : δ) (a : α) (x : Unit) => f c a) init t.inner
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Monadically computes a value by folding the given function over the elements in the tree set in ascending order.
Equations
- Std.TreeSet.foldM f init t = Std.TreeSet.foldlM f init t
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Folds the given function over the elements of the tree set in ascending order.
Equations
- Std.TreeSet.foldl f init t = Std.TreeMap.foldl (fun (c : δ) (a : α) (x : Unit) => f c a) init t.inner
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Folds the given function over the elements of the tree set in ascending order.
Equations
- Std.TreeSet.fold f init t = Std.TreeSet.foldl f init t
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Monadically computes a value by folding the given function over the elements in the tree set in descending order.
Equations
- Std.TreeSet.foldrM f init t = Std.TreeMap.foldrM (fun (a : α) (x : Unit) (acc : δ) => f a acc) init t.inner
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Folds the given function over the elements of the tree set in descending order.
Equations
- Std.TreeSet.foldr f init t = Std.TreeMap.foldr (fun (a : α) (x : Unit) (acc : δ) => f a acc) init t.inner
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Folds the given function over the elements of the tree set in descending order.
Equations
- Std.TreeSet.revFold f init t = Std.TreeSet.foldr (fun (a : α) (acc : δ) => f acc a) init t
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Partitions a tree set into two tree sets based on a predicate.
Equations
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Carries out a monadic action on each element in the tree set in ascending order.
Equations
- Std.TreeSet.forM f t = Std.TreeMap.forM (fun (a : α) (x : Unit) => f a) t.inner
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Support for the for loop construct in do blocks. The iteration happens in ascending
order.
Equations
- Std.TreeSet.forIn f init t = Std.TreeMap.forIn (fun (a : α) (x : Unit) (c : δ) => f a c) init t.inner
Instances For
Equations
- Std.TreeSet.instForM = { forM := fun [Monad m] (t : Std.TreeSet α cmp) (f : α → m PUnit) => Std.TreeSet.forM f t }
Transforms a list into a tree set.
Equations
- Std.TreeSet.ofList l cmp = { inner := Std.TreeMap.unitOfList l cmp }
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Transforms a list into a tree set.
Equations
- Std.TreeSet.fromList l cmp = Std.TreeSet.ofList l cmp
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Transforms an array into a tree set.
Equations
- Std.TreeSet.ofArray a cmp = { inner := Std.TreeMap.unitOfArray a cmp }
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Transforms an array into a tree set.
Equations
- Std.TreeSet.fromArray a cmp = Std.TreeSet.ofArray a cmp
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Returns a set that contains all mappings of t₁ and `t₂.
This function ensures that t₁ is used linearly.
Hence, as long as t₁ is unshared, the performance characteristics follow the following imperative
description: Iterate over all mappings in t₂, inserting them into t₁.
Hence, the runtime of this method scales logarithmically in the size of t₁ and linearly in the
size of t₂ as long as t₁ is unshared.
Equations
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Inserts multiple elements into the tree set by iterating over the given collection and calling
insert. If the same element (with respect to cmp) appears multiple times, the first occurrence
takes precedence.
Note: this precedence behavior is true for TreeSet and TreeSet.Raw. The insertMany function on
TreeMap, DTreeMap, TreeMap.Raw and DTreeMap.Raw behaves differently: it will prefer the last
appearance.
Equations
- t.insertMany l = { inner := t.inner.insertManyIfNewUnit l }
Instances For
Equations
- Std.TreeSet.instRepr = { reprPrec := fun (m : Std.TreeSet α cmp) (prec : Nat) => Repr.addAppParen (Std.Format.text "Std.TreeSet.ofList " ++ repr m.toList) prec }