gnu.prolog.vm.interpreter
Class ExecutionState

java.lang.Object
  gnu.prolog.vm.interpreter.ExecutionState

public class ExecutionState
extends Object

execution state class

Field Summary

Term[]	args arguments
static int	BACKTRACK instruction return code indicating need for backtracking
Term[]	environment current environment
Interpreter	interpreter current interpreter
static int	JUMP instruction return code indicating success.
int	jumpPosition current position
static int	NEXT instruction return code indicating success.
List<Term>	pushdown pushdown stack, used for unification and calls
static int	RETURN instruction return code indicating success.
BacktrackInfo	startBacktrackInfo current backtrack info, only active on backtracking

Constructor Summary

ExecutionState()

Method Summary

CallBacktrackInfo	getCallBacktrackInfo(int codePosition, Term[] args, PrologCode code, CompoundTermTag tag) get BacktrackInfo for call instruction.
EnterBacktrackInfo	getEnterBacktrackInfo() get enter backtrack info
Term	getEnvironment(int environmentIndex) get term from environment
LeaveBacktrackInfo	getLeaveBacktrackInfo() get leave backtrack info
RetryBacktrackInfo	getRetryBacktrackInfo(int retryPosition) get BacktrackInfo for try family instructions.
BacktrackInfo	peekBacktrackInfo() peek backtrack info w/o popping it
BacktrackInfo	popBacktrackInfo() pop backtrack info from stack
Term	popPushDown() pop term from pushdown stack
void	pushBacktrackInfo(BacktrackInfo cbi) push backtrack info to stack
void	pushPushDown(Term term) push term to pushdown stack
void	putEnvironment(int environmentIndex, Term term) put term to environment

Methods inherited from class java.lang.Object

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

Field Detail

BACKTRACK

public static final int BACKTRACK

instruction return code indicating need for backtracking

See Also:

Constant Field Values

NEXT

public static final int NEXT

instruction return code indicating success. backtrack information may or not be created

See Also:

Constant Field Values

JUMP

public static final int JUMP

instruction return code indicating success. jump to position in instruction pointer needed

See Also:

Constant Field Values

RETURN

public static final int RETURN

instruction return code indicating success. return from function needed.

See Also:

Constant Field Values

interpreter

public Interpreter interpreter

current interpreter

startBacktrackInfo

public BacktrackInfo startBacktrackInfo

current backtrack info, only active on backtracking

environment

public Term[] environment

current environment

pushdown

public List<Term> pushdown

pushdown stack, used for unification and calls

jumpPosition

public int jumpPosition

current position

args

public Term[] args

arguments

Constructor Detail

ExecutionState

public ExecutionState()

Method Detail

popBacktrackInfo

public BacktrackInfo popBacktrackInfo()

pop backtrack info from stack

peekBacktrackInfo

public BacktrackInfo peekBacktrackInfo()

peek backtrack info w/o popping it

pushBacktrackInfo

public void pushBacktrackInfo(BacktrackInfo cbi)

push backtrack info to stack

getCallBacktrackInfo

public CallBacktrackInfo getCallBacktrackInfo(int codePosition,
                                              Term[] args,
                                              PrologCode code,
                                              CompoundTermTag tag)

get BacktrackInfo for call instruction.

Parameters:

codePosition -

args -

code -

tag -

Returns:

getRetryBacktrackInfo

public RetryBacktrackInfo getRetryBacktrackInfo(int retryPosition)

get BacktrackInfo for try family instructions.

Parameters:

retryPosition -

Returns:

popPushDown

public Term popPushDown()

pop term from pushdown stack

Returns:

pushPushDown

public void pushPushDown(Term term)

push term to pushdown stack

Parameters:

term -

getEnvironment

public Term getEnvironment(int environmentIndex)

get term from environment

Parameters:

environmentIndex -

Returns:

putEnvironment

public void putEnvironment(int environmentIndex,
                           Term term)

put term to environment

Parameters:

environmentIndex -

term -

getLeaveBacktrackInfo

public LeaveBacktrackInfo getLeaveBacktrackInfo()

get leave backtrack info

Returns:

getEnterBacktrackInfo

public EnterBacktrackInfo getEnterBacktrackInfo()

get enter backtrack info

Returns: