org.eigenbase.util.mapping
Enum MappingType

java.lang.Object
  java.lang.Enum<MappingType>
      org.eigenbase.util.mapping.MappingType

All Implemented Interfaces:

Serializable, Comparable<MappingType>

public enum MappingType
extends Enum<MappingType>

Describes the type of a mapping, from the most general MultiFunction (every element in the source and target domain can participate in many mappings) to the most retricted Bijection (every element in the source and target domain must be paired with precisely one element in the other domain).

Some common types:

• A surjection is a mapping if every target has at least one source; also known as an 'onto' mapping.
• A mapping is a partial function if every source has at most one target.
• A mapping is a function if every source has precisely one target.
• An injection is a mapping where a target has at most one source; also somewhat confusingly known as a 'one-to-one' mapping.
• A bijection is a mapping which is both an injection and a surjection. Every source has precisely one target, and vice versa.

Once you know what type of mapping you want, call Mappings.create(MappingType, int, int) to create an efficient implementation of that mapping.

Since:

Mar 24, 2006

Version:

$Id: //open/dev/farrago/src/org/eigenbase/util/mapping/MappingType.java#10 $

Author:

jhyde

Enum Constant Summary

Bijection

Eleven

Fourteen

Function

Injection

InverseFunction
An inverse function has a source for every target, but a source might have 0, 1 or more targets.

InverseInjection

InversePartialFunction

InversePartialInjection

InverseSurjection
An inverse surjection has a source for every target, and no source has more than one target.

MultiFunction

PartialFunction

PartialInjection

PartialSurjection
A partial surjection has no more than one source for any target, and no more than one target for any source.

Surjection

Ten

Field Summary

private int	inverseOrdinal
private static int	MultipleSource Allow more than one source for a given target.
private static int	MultipleTarget Allow more than one target for a given source.
private static int	OptionalSource Allow less than one source for a given target.
private static int	OptionalTarget Allow less than one target for a given source.

Method Summary

MappingType	inverse()
boolean	isA(MappingType mappingType) Returns whether this mapping type is (possibly a weaker form of) a given mapping type.
boolean	isBijection() A mapping is a bijection if it is a surjection and it is an injection.
boolean	isFunction() A mapping is a total function if every source has precisely one target.
boolean	isInjection() A mapping is an injection if it is a function and no target has more than one source.
boolean	isMandatorySource() Constraint that every target has at least one source.
boolean	isMandatoryTarget() Constraint that every source has at least one target.
boolean	isPartialFunction() A mapping is a partial function if every source has at most one target.
boolean	isSingleSource() Constraint that every target has at most one source.
boolean	isSingleTarget() Constraint that every source has at most one target.
boolean	isSurjection() A mapping is a surjection if it is a function and every target has at least one source.
static MappingType	valueOf(String name) Returns the enum constant of this type with the specified name.
static MappingType[]	values() Returns an array containing the constants of this enum type, in the order they're declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

Bijection

public static final MappingType Bijection

Surjection

public static final MappingType Surjection

Injection

public static final MappingType Injection

Function

public static final MappingType Function

InverseSurjection

public static final MappingType InverseSurjection

An inverse surjection has a source for every target, and no source has more than one target.

PartialSurjection

public static final MappingType PartialSurjection

A partial surjection has no more than one source for any target, and no more than one target for any source.

PartialInjection

public static final MappingType PartialInjection

PartialFunction

public static final MappingType PartialFunction

InverseInjection

public static final MappingType InverseInjection

InversePartialInjection

public static final MappingType InversePartialInjection

Ten

public static final MappingType Ten

Eleven

public static final MappingType Eleven

InverseFunction

public static final MappingType InverseFunction

An inverse function has a source for every target, but a source might have 0, 1 or more targets.

Obeys the constaints isMandatorySource(), isSingleSource().

Similar types:

• InverseSurjection is stronger (a source may not have multiple targets);
• InversePartialFunction is weaker (a target may have 0 or 1 sources).

InversePartialFunction

public static final MappingType InversePartialFunction

Fourteen

public static final MappingType Fourteen

MultiFunction

public static final MappingType MultiFunction

Field Detail

inverseOrdinal

private final int inverseOrdinal

OptionalSource

private static final int OptionalSource

Allow less than one source for a given target.

See Also:

Constant Field Values

MultipleSource

private static final int MultipleSource

Allow more than one source for a given target.

See Also:

Constant Field Values

OptionalTarget

private static final int OptionalTarget

Allow less than one target for a given source.

See Also:

Constant Field Values

MultipleTarget

private static final int MultipleTarget

Allow more than one target for a given source.

See Also:

Constant Field Values

Method Detail

values

public static final MappingType[] values()

Returns an array containing the constants of this enum type, in the order they're declared. This method may be used to iterate over the constants as follows:

for(MappingType c : MappingType.values())
        System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they're declared

valueOf

public static MappingType valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

inverse

public MappingType inverse()

isA

public boolean isA(MappingType mappingType)

Returns whether this mapping type is (possibly a weaker form of) a given mapping type.

For example, a Bijection is a Function, but not every {link #Function} is a Bijection.

isFunction

public boolean isFunction()

A mapping is a total function if every source has precisely one target.

isPartialFunction

public boolean isPartialFunction()

A mapping is a partial function if every source has at most one target.

isSurjection

public boolean isSurjection()

A mapping is a surjection if it is a function and every target has at least one source.

isInjection

public boolean isInjection()

A mapping is an injection if it is a function and no target has more than one source. (In other words, every source has precisely one target.)

isBijection

public boolean isBijection()

A mapping is a bijection if it is a surjection and it is an injection. (In other words,

isMandatoryTarget

public boolean isMandatoryTarget()

Constraint that every source has at least one target.

isSingleTarget

public boolean isSingleTarget()

Constraint that every source has at most one target.

isMandatorySource

public boolean isMandatorySource()

Constraint that every target has at least one source.

isSingleSource

public boolean isSingleSource()

Constraint that every target has at most one source.