ptolemy.actor.util

Class GLBFunction

java.lang.Object

ptolemy.data.type.MonotonicFunction

ptolemy.actor.util.GLBFunction

All Implemented Interfaces:

InequalityTerm

public class GLBFunction
extends MonotonicFunction

This class implements a monotonic function that returns the greatest lower bound (GLB) of its arguments. These arguments are the port type variables of the destination ports of the TypedIOPort passed to the constructor. This function is used to define a type constraint asserting that the type of the output of this port is greater than or equal to the GLB of its destinations.

NOTE: It may seem counterintuitive that the constraint is "greater than or equal to" rather than "less than or equal to". But the latter constraint is already implied by the connections, since the output port type is required to be less than or equal to each destination port type. The combination of these constraints has the effect of setting the type of the output equal to the GLB of the types of the destination ports. This resolved type is, in fact, the most specific type that satisfies the constraints of all the downstream ports.

Since:

Ptolemy II 10.0

Version:

$Id: GLBFunction.java$

Author:

Edward A. Lee, Marten Lohstroh

Accepted Rating:

Red (cxh)

Proposed Rating:

Red (eal)

Field Summary

Fields

Modifier and Type	Field and Description
protected InequalityTerm[]	_cachedTerms The types terms found in destination ports.
protected java.util.Set<Type>	_cachedTypes The constant types found in destination ports.
protected long	_previousWorkspaceVersion The workspace version number at time of last update of arguments.
protected TypedIOPort	_sourcePort The source port.

Constructor Summary

Constructors

Constructor and Description
GLBFunction(TypedIOPort sourcePort) Construct a GLBFunction that finds the greatest lower bound of the type variable of the destination ports connected to the TypedIOPort that is given as an argument.

Method Summary

Modifier and Type	Method and Description
protected void	_updateArguments() Update the arguments used in getValue(), which are the InequalityTerms and Types of the destination ports.
Type[]	getConstants() Return the type constants for this function, which are the type constant types for all the destination ports.
java.lang.Object	getValue() Return the current value of this monotonic function.
InequalityTerm[]	getVariables() Return the type variables for this function, which are the type variables for all the destination ports.
java.lang.String	toString() Provide a more descriptive string representation.

Methods inherited from class ptolemy.data.type.MonotonicFunction

getAssociatedObject, getVerboseString, initialize, isSettable, isValueAcceptable, setValue

Methods inherited from class java.lang.Object

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

Field Detail

_cachedTypes

protected java.util.Set<Type> _cachedTypes

The constant types found in destination ports.

_cachedTerms

protected InequalityTerm[] _cachedTerms

The types terms found in destination ports.

_previousWorkspaceVersion

protected long _previousWorkspaceVersion

The workspace version number at time of last update of arguments.

_sourcePort

protected TypedIOPort _sourcePort

The source port.

Constructor Detail

GLBFunction

public GLBFunction(TypedIOPort sourcePort)

Construct a GLBFunction that finds the greatest lower bound of the type variable of the destination ports connected to the TypedIOPort that is given as an argument. If the boolean argument inside is true then the port is required to be an input port and the arguments for this GLBFunction will be the inside destination ports. Otherwise, the port is required to be an output port and the arguments for this GLBFunction will be the outside destination ports.

Parameters:

sourcePort - The port connected to the ports of which their type variables are used to calculate the greatest lower bound.

Method Detail

getValue

public java.lang.Object getValue()
                          throws IllegalActionException

Return the current value of this monotonic function.

Specified by:

getValue in interface InequalityTerm

Specified by:

getValue in class MonotonicFunction

Returns:

A Type.

Throws:

IllegalActionException - If thrown while getting the value of the cached terms.

See Also:

MonotonicFunction.setValue(Object)

getVariables

public InequalityTerm[] getVariables()

Return the type variables for this function, which are the type variables for all the destination ports.

Specified by:

getVariables in interface InequalityTerm

Specified by:

getVariables in class MonotonicFunction

Returns:

An array of InequalityTerms.

getConstants

public Type[] getConstants()

Return the type constants for this function, which are the type constant types for all the destination ports.

Returns:

An array of Types.

_updateArguments

protected void _updateArguments()

Update the arguments used in getValue(), which are the InequalityTerms and Types of the destination ports. The arguments are only updated if the workspace version has changed.

toString

public java.lang.String toString()

Provide a more descriptive string representation.

Overrides:

toString in class MonotonicFunction

Returns:

A description of this term.