au.edu.monash.csse.tonyj.cider.interpreter
Class Interpreter

java.lang.Object
  |
  +--Interpreter

All Implemented Interfaces:

ConstraintVariableListener, java.util.EventListener, java.io.Serializable

public abstract class Interpreter

extends java.lang.Object

implements ConstraintVariableListener, java.io.Serializable

The Interpreter is the main control class in the CIDER toolkit that maintains a parse forest representation of a diagram, is responsible for applying productions, and also controls the application of transformations. It as an abstract base class that is extended by a grammar-specific class that is responsible for implementing functionality that is grammar dependent. This grammar-specific class is produced by the CIDER compiler. Note that when an instance of this class is created, auto forest checking and auto constraint solving are initially turned on.

See Also:

Serialized Form

Method Summary

boolean	addConstraint(Constraint c) Adds a constraint to the multi-way constraint solver.
void	addGrammarSymbolListener(GrammarSymbolListener gsl) Adds an listener to listen for grammar symbol events.
boolean	addTerminalSymbol(GrammarSymbol symbol) Adds a terminal symbol to the parse forest.
abstract boolean	applyTransformation(int transformation) Applies a specified transformation to the parse forest at the first valid location it finds.
abstract boolean	applyTransformationInParallel(int transformation) Applies a specified transformation to the parse forest in parallel.
void	checkForest() Checks all productions and updates all attributes in the parse forest that require it.
void	disableUndo() Turns off the ability to undo actions.
void	enableUndo() Turns on the ability to undo actions.
abstract void	evaluateProductionRules() Explicitly calls the grammar-specific interpreter to evaluate the production rules.
ConstraintSolver	getConstraintSolver() Returns the multi-way constraint solver associated with the interpreter.
java.util.Set	getTerminalSymbols() Returns a set containing all terminal symbols in the parse forest.
int	getUndoIndex() Returns the index to the most recent action recorded on the undo action list.
boolean	isAutoConstraintSolvingOn() Returns true if auto constraint solving is on, false otherwise.
boolean	isAutoForestCheckingOn() Returns true if auto forest checking is on, false otherwise.
boolean	isUndoEnabled() Returns true if the undo feature is currently enabled, false otherwise.
boolean	isUpToDate() Returns true if the parse forest is up to date, false otherwise.
boolean	load(java.lang.String filename) Restores a previously saved state.
void	printForest(java.io.PrintStream stream) Prints the parse forest.
void	reevaluateForest() Reevaluates all productions in the parse forest.
boolean	removeConstraint(Constraint c) Removes a constraint from the multi-way constraint solver.
void	removeGrammarSymbolListener(GrammarSymbolListener gsl) Removes a listener that listens for grammar symbol events.
boolean	removeTerminalSymbol(GrammarSymbol symbol) Removes a terminal symbol from the parse forest.
boolean	save(java.lang.String filename) Saves the current state.
void	setAutoConstraintSolving(boolean on) Allows auto constraint solving to be turned on or off.
void	setAutoForestChecking(boolean on) Allows auto forest checking to be turned on or off.
static void	setLoggingLevel(java.util.logging.Level level) Allows the logging level for the CIDER logger to be set.
void	solve() Calls the solver to solve all constraints.
boolean	undoActions(int index) Will undo actions that occurred after a specific time, as indicated by the index value.
void	variableModified(ConstraintVariableEvent event) Implemented as part of the ConstraintVariableListener interface.

Methods inherited from class java.lang.Object

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

Method Detail

setLoggingLevel

public static void setLoggingLevel(java.util.logging.Level level)

Allows the logging level for the CIDER logger to be set. By default, the logging level is set to Level.INFO. Logging can be turned off by using Level.OFF, and all messages will be logged if Level.ALL is used.

Parameters:

level - The logging level to be set.

evaluateProductionRules

public abstract void evaluateProductionRules()

Explicitly calls the grammar-specific interpreter to evaluate the production rules.

applyTransformation

public abstract boolean applyTransformation(int transformation)
                                     throws java.lang.IllegalArgumentException

Applies a specified transformation to the parse forest at the first valid location it finds.

Parameters:

transformation - The transformation to be applied.

Returns:

true if the transformation was successful, false otherwise.

Throws:

java.lang.IllegalArgumentException - If an unknown transformation is specified.

applyTransformationInParallel

public abstract boolean applyTransformationInParallel(int transformation)
                                               throws java.lang.IllegalArgumentException

Applies a specified transformation to the parse forest in parallel. That is, it will find all the locations in the parse forest where the transformation can be applied, and then in a single step apply the transformation at all of these locations.

Parameters:

transformation - The transformation to be applied.

Returns:

true if the transformation was successful, false otherwise.

Throws:

java.lang.IllegalArgumentException - If an unknown transformation is specified, or a a transformation is specified that cannot be applied in parallel (such as a compound transformation).

getTerminalSymbols

public java.util.Set getTerminalSymbols()

Returns a set containing all terminal symbols in the parse forest.

addTerminalSymbol

public boolean addTerminalSymbol(GrammarSymbol symbol)

Adds a terminal symbol to the parse forest. If auto forest checking is turned on, the forest will be updated as necessary with the symbols from invalid productions removed, and the symbols from any new valid productions added. If successful, an event detailing this action will be launched.

Parameters:

symbol - The symbol to be added.

Returns:

true if successful, false if the symbol is not a terminal symbol, or is already present in the parse forest.

removeTerminalSymbol

public boolean removeTerminalSymbol(GrammarSymbol symbol)

Removes a terminal symbol from the parse forest. If auto forest checking is turned on, the forest will be updated as necessary with the symbols from invalid productions removed, and the symbols from any new valid productions added. If successful, an event detailing this action will be launched.

Parameters:

symbol - The symbol to be removed.

Returns:

true if successful, false if the symbol is not a terminal symbol, or is not present in the parse forest.

getConstraintSolver

public ConstraintSolver getConstraintSolver()

Returns the multi-way constraint solver associated with the interpreter. If no constraint solver is being used, null is returned.

addConstraint

public boolean addConstraint(Constraint c)

Adds a constraint to the multi-way constraint solver.

Parameters:

c - The constraint to be added.

Returns:

true if successful, false if no constraint solver is present or the solver would not accept the constraint.

removeConstraint

public boolean removeConstraint(Constraint c)

Removes a constraint from the multi-way constraint solver.

Parameters:

c - The constraint to be removed.

Returns:

true if successful, false if no constraint solver is present or the solver could not remove the constraint.

solve

public void solve()

Calls the solver to solve all constraints. This method should be called if constraints have been added to or removed. Note that it will only work if auto constraint checking is turned on.

printForest

public void printForest(java.io.PrintStream stream)

Prints the parse forest. Primarily for debugging purposes.

Parameters:

stream - The output stream where the text is sent to.

isUpToDate

public boolean isUpToDate()

Returns true if the parse forest is up to date, false otherwise.

addGrammarSymbolListener

public void addGrammarSymbolListener(GrammarSymbolListener gsl)

Adds an listener to listen for grammar symbol events. Events are launched when symbols are added to or removed from the parse forest, and when their attributes are modified.

Parameters:

gsl - The listener to be added.

removeGrammarSymbolListener

public void removeGrammarSymbolListener(GrammarSymbolListener gsl)

Removes a listener that listens for grammar symbol events. Events are launched when symbols are added to or removed from the parse forest, and when their attributes are modified.

Parameters:

gsl - The listener to be removed.

isAutoForestCheckingOn

public boolean isAutoForestCheckingOn()

Returns true if auto forest checking is on, false otherwise. Auto forest checking means that each change that is made to the forest (via a symbol being added, removed or modified), will result in checks to ensure that the forest is in a valid state and up to date.

setAutoForestChecking

public void setAutoForestChecking(boolean on)

Allows auto forest checking to be turned on or off. Auto forest checking means that each change that is made to the forest (via a symbol being added, removed or modified), will result in checks to ensure that the forest is in a valid state and up to date. It should normally be turned on.

Parameters:

on - true to turn on, false to turn off.

isAutoConstraintSolvingOn

public boolean isAutoConstraintSolvingOn()

Returns true if auto constraint solving is on, false otherwise. Auto constraint solving means that the multi-way constraint solver will automatically enforce any constraints that it is responsible for, ensuring that the parse forest remains in a valid state.

setAutoConstraintSolving

public void setAutoConstraintSolving(boolean on)

Allows auto constraint solving to be turned on or off. Auto constraint solving means that the multi-way constraint solver will automatically enforce any constraints that it is responsible for, ensuring that the parse forest remains in a valid state. It should normally be turned on.

Parameters:

on - true to turn on, false to turn off.

checkForest

public void checkForest()

Checks all productions and updates all attributes in the parse forest that require it. If auto forest checking is turned on, this method will be called automatically when needed.

reevaluateForest

public void reevaluateForest()

Reevaluates all productions in the parse forest.

variableModified

public void variableModified(ConstraintVariableEvent event)

Implemented as part of the ConstraintVariableListener interface. Listens for when a constraint variable has been modified by the multi-way constraint solver.

Specified by:

variableModified in interface ConstraintVariableListener

Parameters:

event - Contains details of the event.

save

public boolean save(java.lang.String filename)

Saves the current state. Currently implemented using Java Serialization.

Parameters:

filename - The name of the file where the state will be saved to.

Returns:

true if successful, false otherwise.

load

public boolean load(java.lang.String filename)

Restores a previously saved state. Currently implemented using Java Serialization. Note that this method clears the current state.

Parameters:

filename - The name of the file that contains the saved state.

Returns:

true if successful, false otherwise.

isUndoEnabled

public boolean isUndoEnabled()

Returns true if the undo feature is currently enabled, false otherwise.

enableUndo

public void enableUndo()

Turns on the ability to undo actions. Since storing user actions takes up memory, the undo feature should only be enabled when necessary.

disableUndo

public void disableUndo()

Turns off the ability to undo actions.

getUndoIndex

public int getUndoIndex()

Returns the index to the most recent action recorded on the undo action list. Then, if further actions are carried out, it will possible to later undo all actions that occurred after the one whose index has been obtained, without going any further back (using the undoActions(int) method).

undoActions

public boolean undoActions(int index)

Will undo actions that occurred after a specific time, as indicated by the index value. Note that the undo feature allows for the fact that constraint variables may have been changed by the multi-way constraint solver.

Parameters:

index - The index in the undo action list (obtained from getUndoIndex()).

Returns:

true if successful, false if undo is not enabled, or an invalid index value is given.