uk.ac.sheffield.vtts.model

Class Constant

java.lang.Object

uk.ac.sheffield.vtts.model.Element

uk.ac.sheffield.vtts.model.Named

uk.ac.sheffield.vtts.model.Expression

uk.ac.sheffield.vtts.model.Parameter

uk.ac.sheffield.vtts.model.Constant

public class Constant
extends Parameter

Constant is a kind of parameter standing for some fixed constant value. Constant represents a symbolic constant that is bound to a literal value. The Constant is typically named according to the bound value, such that "zero" represents the value 0, "true" represents the value true and "emptyList" represents an empty list. The bound value is supplied as an XML content string and is converted to a strongly-typed bound value when the Constant is first evaluated. Empty content is always interpreted as a default bound value, according to the type of the Constant. A Constant is therefore always bound.

Version:

Broker@Cloud 1.0

Author:

Anthony J H Simons

Field Summary

Fields inherited from class uk.ac.sheffield.vtts.model.Parameter

bound, content, value

Fields inherited from class uk.ac.sheffield.vtts.model.Expression

factory, type

Fields inherited from class uk.ac.sheffield.vtts.model.Named

name

Constructor Summary

Constructors

Constructor and Description
Constant() Creates a default Constant parameter.
Constant(java.lang.String name, java.lang.String type) Creates a Constant parameter with the given name and type.

Method Summary

Methods

Modifier and Type	Method and Description
void	assign(java.lang.Object value) Reports an attempt to assign to this Constant as an error.
java.lang.Boolean	getBound() Degenerate method to fetch the bound status for marshalling.
boolean	isAssignable() Reports whether this Constant is assignable.
boolean	isBottom() Reports whether this Constant is the bottom element of its type.
void	rebind(java.lang.Object value) Degenerate method to rebind this Constant to a new value.
Constant	setBound(boolean value) Degenerate method to set the bound status of this Constant.
void	unbind() Degenerate method to unbind this Constant.

Methods inherited from class uk.ac.sheffield.vtts.model.Parameter

evaluate, getContent, isBound, rebind, resolve, setContent, snapshot, toString

Methods inherited from class uk.ac.sheffield.vtts.model.Expression

equals, getName, getType, hashCode, isOrdered, setType

Methods inherited from class uk.ac.sheffield.vtts.model.Named

setName, setName

Methods inherited from class uk.ac.sheffield.vtts.model.Element

safeEquals, safeHashCode, semanticError

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

Constant

public Constant()

Creates a default Constant parameter.

Constant

public Constant(java.lang.String name,
        java.lang.String type)

Creates a Constant parameter with the given name and type.

Parameters:

name - the name of this Constant.

type - the type of this Constant.

Method Detail

setBound

public Constant setBound(boolean value)

Degenerate method to set the bound status of this Constant.

Overrides:

setBound in class Parameter

Parameters:

value - is ignored, since Constants are always bound.

Returns:

this Constant.

getBound

public java.lang.Boolean getBound()

Degenerate method to fetch the bound status for marshalling. Constants do not need to marshal their bound status, since they are always bound.

Overrides:

getBound in class Parameter

Returns:

null.

unbind

public void unbind()

Degenerate method to unbind this Constant. This is a null operation, since Constants are never unbound, but always keep their bound value. Likewise, the stored content String for a Constant is never deleted.

Overrides:

unbind in class Parameter

rebind

public void rebind(java.lang.Object value)

Degenerate method to rebind this Constant to a new value. This is a null operation, since constants cannot be rebound to a different value other than the one they had at creation.

Overrides:

rebind in class Parameter

Parameters:

value - the value to bind.

isBottom

public boolean isBottom()

Reports whether this Constant is the bottom element of its type. This is true for the null Character, the empty String, Set, List or Map; and false for all other values. This judgement is used when refining the partitions of a comparison, to decide whether lessThan(x, y) is a meaningful partition.

Overrides:

isBottom in class Expression

Returns:

true, if this Constant is the bottom element of its type.

isAssignable

public boolean isAssignable()

Reports whether this Constant is assignable. Returns false, since it is illegal to re-assign a new value to a Constant.

Overrides:

isAssignable in class Parameter

Returns:

false, always.

assign

public void assign(java.lang.Object value)

Reports an attempt to assign to this Constant as an error.

Overrides:

assign in class Parameter

Parameters:

value - the value to assign.