org.apache.calcite.util

Class EquivalenceSet<E extends Comparable<E>>

java.lang.Object

org.apache.calcite.util.EquivalenceSet<E>

Type Parameters:

E - Element type

public class EquivalenceSet<E extends Comparable<E>>
extends Object

Set of elements organized into equivalence classes.

Elements are equivalent by the rules of a mathematical equivalence relation:

Reflexive

Every element e is equivalent to itself

Symmetric

If e is equivalent to f, then f is equivalent to e

Transitive

If e is equivalent to f, and f is equivalent to g, then e is equivalent to g

For any given pair of elements, answers in O(log N) (two hash-table lookups) whether they are equivalent to each other.

Constructor Summary

Constructors

Constructor and Description
EquivalenceSet()

Method Summary

Modifier and Type	Method and Description
E	add(E e) Adds an element, and returns the element (which is its own parent).
boolean	areEquivalent(E e, E f) Returns whether two elements are in the same equivalence class.
int	classCount() Returns the number of equivalence classes in this equivalence set.
void	clear() Removes all elements in this equivalence set.
E	equiv(E e, E f) Marks two elements as equivalent.
SortedMap<E,SortedSet<E>>	map() Returns a map of the canonical element in each equivalence class to the set of elements in that class.
int	size() Returns the number of elements in this equivalence set.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

EquivalenceSet

public EquivalenceSet()

Method Detail

add

public E add(E e)

Adds an element, and returns the element (which is its own parent). If already present, returns the element's parent.

equiv

public E equiv(E e,
               E f)

Marks two elements as equivalent. They may or may not be registered, and they may or may not be equal.

areEquivalent

public boolean areEquivalent(E e,
                             E f)

Returns whether two elements are in the same equivalence class. Returns false if either or both of the elements are not registered.

map

public SortedMap<E,SortedSet<E>> map()

Returns a map of the canonical element in each equivalence class to the set of elements in that class. The keys are sorted in natural order, as are the elements within each key.

clear

public void clear()

Removes all elements in this equivalence set.

size

public int size()

Returns the number of elements in this equivalence set.

classCount

public int classCount()

Returns the number of equivalence classes in this equivalence set.