wyautl_old.lang

Class Automaton

java.lang.Object

wyautl_old.lang.Automaton

public final class Automaton
extends Object

A finite-state automaton for representing Whiley types. This is a machine for accepting matching inputs of a given language. An automaton is a directed graph whose nodes and edges are referred to as states and transitions. Each state has a "kind" which determines how the state behaves on given inputs. For example, a state with "OR" kind might accept an input if either of its children does; in contrast, and state of "AND" kind might accept an input only if all its children does.

The organisation of children is done according to two approaches: deterministic and non-deterministic. In the deterministic approach, the ordering of children is important; in the non-deterministic approach, the ordering of children is not important. A flag is used to indicate whether a state is deterministic or not.

Aside from having a particular kind, each state may also have supplementary material. This can be used, for example, to effectively provide labelled transitions. Another use of this might be to store a given string which must be matched.

NOTE: In the internal representation of automata, leaf states may be not be represented as actual nodes. This will occur if the leaf node does not include any supplementary data, and is primarily for space and performance optimisation. In such case, the node is represented as a child node using a negative index.

Author:

David J. Pearce

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Automaton.State Represents a state in an automaton.

Field Summary

Fields

Modifier and Type	Field and Description
static int[]	NOCHILDREN The following constant is used simply to prevent unnecessary memory allocations.
Automaton.State[]	states

Constructor Summary

Constructors

Constructor and Description
Automaton(Automaton.State... states)
Automaton(Automaton automaton)
Automaton(List<Automaton.State> states)

Method Summary

Modifier and Type	Method and Description
boolean	equals(Object o) This method compares two compound types to test whether they are identical.
int	hashCode() Determine the hashCode of a type.
int	size()
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

states

public Automaton.State[] states

NOCHILDREN

public static final int[] NOCHILDREN

The following constant is used simply to prevent unnecessary memory allocations.

Constructor Detail

Automaton

public Automaton(Automaton.State... states)

Automaton

public Automaton(List<Automaton.State> states)

Automaton

public Automaton(Automaton automaton)

Method Detail

size

public int size()

hashCode

public int hashCode()

Determine the hashCode of a type.

Overrides:

hashCode in class Object

equals

public boolean equals(Object o)

This method compares two compound types to test whether they are identical. Observe that it does not perform an isomorphism test. Thus, two distinct types which are structurally isomorphic will not be considered equal under this method. NOTE: to test whether two types are structurally isomorphic, using the isomorphic(t1,t2) method.

Overrides:

equals in class Object

toString

public String toString()

Overrides:

toString in class Object