gnu.prolog.vm.interpreter.instruction
Class Instruction

java.lang.Object
  gnu.prolog.vm.interpreter.instruction.Instruction

All Implemented Interfaces:

Installable

Direct Known Subclasses:

IAllocate, ICall, ICreateCompoundTerm, ICreateVariable, ICut, IDup, IFail, IJump, IPop, IPushArgument, IPushConstant, IPushEnvironment, IRestoreState, IReturn, ISaveCut, ISaveState, IStoreEnvironment, IThrow, ITrue, ITrustMe, IUnify, RetryInstruction

public abstract class Instruction
extends Object
implements Installable

base call for instruction

Field Summary

int	codePosition code position of instruction

Constructor Summary

Instruction()

Method Summary

abstract int	execute(ExecutionState state, BacktrackInfo bi) execute instruction
void	install(Environment env) install instruction to environment
void	uninstall(Environment env) uninstall instruction from environment

Methods inherited from class java.lang.Object

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

Field Detail

codePosition

public int codePosition

code position of instruction

Constructor Detail

Instruction

public Instruction()

Method Detail

execute

public abstract int execute(ExecutionState state,
                            BacktrackInfo bi)
                     throws PrologException

execute instruction

Parameters:

state - state within which instruction will be executed

bi -

Returns:

ExecutionState.{BACKTRACK,NEXT,JUMP,RETURN}: instruction to caller how to execute next instruction

Throws:

PrologException - if code is throwing prolog exception

install

public void install(Environment env)

install instruction to environment

Specified by:

install in interface Installable

Parameters:

env - Environment to install the predicate

uninstall

public void uninstall(Environment env)

uninstall instruction from environment

Specified by:

uninstall in interface Installable

Parameters:

env - Environment to install the predicate