com.svincent.moksa
Class Rule

java.lang.Object
  |
  +--com.svincent.moksa.WamObject
        |
        +--com.svincent.moksa.Rule

Direct Known Subclasses:

Builtin.BuiltinRule, CompiledRule, InterpretedRule

public abstract class Rule

extends WamObject

The abstract base class for all Rules.

Constructor Summary

Rule()
Make a new instance of this Rule.

Method Summary

abstract int	getArity() Return the arity of this Rule (i.e.
abstract java.lang.String	getName() Return the name of this Rule in "atom/arity" notation.
abstract PrologTerm	getTerm(PrologFactory factory) Return the Prolog term corresponding to this Rule.
Continuation	invoke(Wam wam) Invoke this Rule.
abstract Continuation	invokeRule(Wam wam) Contains the code which defines what this Rule does.
boolean	isFirstAlternative() true iff this is the first registered alternative.
boolean	isLastAlternative() true iff this is the last registered alternative.
boolean	isOnlyAlternative() true iff this is the only registered alternative.
void	tag(java.io.PrintWriter out) Returns a short, human-readable String describing this Rule.

Methods inherited from class com.svincent.moksa.WamObject

tag

Methods inherited from class java.lang.Object

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

Constructor Detail

Rule

public Rule()

Make a new instance of this Rule. Rules are Singletons: there is one instance of any particular Rule class.

Method Detail

getName

public abstract java.lang.String getName()

Return the name of this Rule in "atom/arity" notation.

getArity

public abstract int getArity()

Return the arity of this Rule (i.e. - the number of parameters it expects).

getTerm

public abstract PrologTerm getTerm(PrologFactory factory)

Return the Prolog term corresponding to this Rule. The term returned is invariably an instance of :-/2: this is a Rule, after all!

isOnlyAlternative

public boolean isOnlyAlternative()

true iff this is the only registered alternative.

isFirstAlternative

public boolean isFirstAlternative()

true iff this is the first registered alternative.

isLastAlternative

public boolean isLastAlternative()

true iff this is the last registered alternative.

invoke

public Continuation invoke(Wam wam)
                    throws PrologException

Invoke this Rule. Does various WAM setup, then calls invokeRule.

See Also:

invokeRule(com.svincent.moksa.Wam)

invokeRule

public abstract Continuation invokeRule(Wam wam)
                                 throws PrologException

Contains the code which defines what this Rule does. Called by invoke.

See Also:

invoke(com.svincent.moksa.Wam)

tag

public void tag(java.io.PrintWriter out)

Returns a short, human-readable String describing this Rule.

Overrides:

tag in class WamObject