parsii.eval

Class Variable

java.lang.Object

parsii.eval.Variable

public class Variable
extends Object

Represents a variable which binds a value to a name.

A variable is resolved or created using a Scope. This ensures that the same name always resolves to the same variable. In contrast to using a Map, reading and writing a variable can be much faster, as it only needs to be resolved once. Reading and writing it, is basically as cheap as a field access.

A variable can be made constant, which will fail all further attempts to change it.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Variable(String name) Creates a new variable.

Method Summary

Modifier and Type	Method and Description
String	getName() Returns the name of the variable.
double	getValue() Returns the value previously set.
boolean	isConstant() Determines if this variable is constant.
void	makeConstant(double value) Sets the given value and marks it as constant.
void	setValue(double value) Sets the value if the variable.
String	toString()
Variable	withValue(double value) Sets the value and returns this.

Methods inherited from class java.lang.Object

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

Constructor Detail

Variable

protected Variable(String name)

Creates a new variable.

Variables should only be created by their surrounding Scope so that all following look-ups yield the same variable.

Parameters:

name - the name of the variable

Method Detail

setValue

public void setValue(double value)

Sets the value if the variable.

Parameters:

value - the new value of the variable

Throws:

IllegalStateException - if the variable is constant

makeConstant

public void makeConstant(double value)

Sets the given value and marks it as constant.

Parameters:

value - the new (and final) value of this variable

getValue

public double getValue()

Returns the value previously set.

Returns:

the value previously set or 0 if the variable is not written yet

toString

public String toString()

Overrides:

toString in class Object

getName

public String getName()

Returns the name of the variable.

Returns:

the name of this variable

isConstant

public boolean isConstant()

Determines if this variable is constant.

Returns:

true if this variable cannot be modified anymore, false otherwise

withValue

public Variable withValue(double value)

Sets the value and returns this.

Parameters:

value - the new value of this variable

Returns:

this for fluent method calls