com.rubecula.jquantity
Class Expression

java.lang.Object
  java.util.AbstractCollection
      java.util.AbstractList
          java.util.Vector
              com.rubecula.jquantity.Expression

All Implemented Interfaces:

java.lang.Cloneable, java.util.Collection, java.util.List, Presentable, java.util.RandomAccess, Replaceable, java.io.Serializable

public class Expression

extends java.util.Vector

implements Replaceable

Class to manage a mathematical expression. It is the Presentable counterpart to SymbolicPresentation. Elements, the order of which is important, are either of:

• a Presentable;
• an Expression (parentheses are "implicit");

Note that although this class is defined in terms of Replaceable (which extends Presentableand java.util.Vector only), nevertheless it uses numerical classes such as BaseNumber and the abstract class of Item. This doesn't seem quite right. // TODO The calculations which use operators on Items and BaseNumbers ought to be defined somewhere else so that this class could be more "pure".

Since:

V_0_3

Version:

$Revision: 1.14 $

Author:

Robin Hillyard

See Also:

Serialized Form

Nested Class Summary

(package private) static class

Expression.ExpressionException Static class to define an exception encountered when parsing a formula.

Nested classes inherited from class java.util.AbstractList

Field Summary

private static Lookupable

$CONSTANTS This Lookupable object is where "constants" that may be required by any expression can be stored.

Fields inherited from class java.util.Vector

capacityIncrement, elementCount, elementData

Fields inherited from class java.util.AbstractList

modCount

Constructor Summary

Expression()
Constructor for an empty formula.

Expression(Presentable presentable)
Constructor for an "anadic" formula of all strings.

Method Summary

static Lookupable	GetConstants()
java.lang.String	getType() This method is primarily for development purposes: it yields the name of the class of the presentable object or, in some cases, the class of the presentable object indirectly referenced.
Presentable	getValue() Method to evaluate this expression.
Presentable	getValue(java.lang.Object ignored) This method takes this Expression and returns its logical equivalent, i.e. it evaluates the expression.
private static Presentable	LookupConstant(java.lang.String s)
static void	main(java.lang.String[] args) Main method for testing this class.
Presentable	makePresentableInstance(Presentation presentation) Instance method to convert a Presentation into a Presentable.
private static Item	OpAnadic(Operator op)
private static Item	OpDyadicComplex(Item current, Operator currentOp, Item number)
private static Item	OpDyadicNonComplex(Item current, Operator currentOp, BaseNumber number) Note that the order of the operands is the reverse of the true order.
private static Item	OpMonadic(Operator op, Item number)
static Presentable	Parse(Presentation presentation) Create a Rational from a Presentation and return it as a Presentable.
static Expression	Parse(SymbolicPresentation presentation, java.lang.String identifier) Translates the SymbolicPresentation representation of an expression into an instance of Expression.
Presentation	present() Convert this Presentable object into a Presentation with default attributes.
Presentation	present(AttrMap attributes) Convert this Presentable object into a Presentation, according to the set of attributes provided.
static void	SetConstants(Lookupable constants)
protected static void	testExpression(java.io.PrintStream out, SymbolicPresentation sp, java.lang.String label)

Methods inherited from class java.util.Vector

add, add, addAll, addAll, addElement, capacity, clear, clone, contains, containsAll, copyInto, elementAt, elements, ensureCapacity, equals, firstElement, get, hashCode, indexOf, indexOf, insertElementAt, isEmpty, lastElement, lastIndexOf, lastIndexOf, remove, remove, removeAll, removeAllElements, removeElement, removeElementAt, removeRange, retainAll, set, setElementAt, setSize, size, subList, toArray, toArray, toString, trimToSize

Methods inherited from class java.util.AbstractList

iterator, listIterator, listIterator

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.util.List

iterator, listIterator, listIterator

Field Detail

$CONSTANTS

private static Lookupable $CONSTANTS

This Lookupable object is where "constants" that may be required by any expression can be stored.

Constructor Detail

Expression

public Expression()

Constructor for an empty formula.

Expression

public Expression(Presentable presentable)

Constructor for an "anadic" formula of all strings.

Parameters:

presentable - the presentable to form this singleton expression.

Method Detail

Parse

public static Expression Parse(SymbolicPresentation presentation,
                               java.lang.String identifier)
                        throws PresentationException

Translates the SymbolicPresentation representation of an expression into an instance of Expression.

Parameters:

presentation - SymbolicPresentation representation to interpret.

identifier - A string with which to identify this Rational.

Returns:

Expression : a new object corresponding to presentation.

Throws:

PresentationException - if the presentation cannot be parsed as an Expression.

LookupConstant

private static Presentable LookupConstant(java.lang.String s)
                                   throws PresentationException,
                                          PresentableException

Throws:

PresentationException

PresentableException

getValue

public Presentable getValue()
                     throws PresentableException

Method to evaluate this expression.

Returns:

a Presentable value corresponding to the current value of this expression.

Throws:

PresentableException - name not be found.

getValue

public Presentable getValue(java.lang.Object ignored)
                     throws PresentableException

This method takes this Expression and returns its logical equivalent, i.e. it evaluates the expression. Note that binding is entirely position, and that the implicit operator is times.

Specified by:

getValue in interface Replaceable

Parameters:

ignored - Not used.

Returns:

a Presentable value corresponding to the value of this expression.

Throws:

PresentableException

present

public Presentation present(AttrMap attributes)
                     throws PresentationException

Convert this Presentable object into a Presentation, according to the set of attributes provided.

Specified by:

present in interface Presentable

Parameters:

attributes - a map of desired attributes for this presentation.

Returns:

an appropriate instance of Presentation.

Throws:

PresentationException - if formula cannot be presented with given attributes.

present

public Presentation present()
                     throws PresentationException

Convert this Presentable object into a Presentation with default attributes.

Returns:

an appropriate instance of Presentation.

Throws:

PresentationException - if formula cannot be presented with given attributes.

getType

public java.lang.String getType()

This method is primarily for development purposes: it yields the name of the class of the presentable object or, in some cases, the class of the presentable object indirectly referenced. The text returned is canonical class name (subclasses may choose to override this).

Specified by:

getType in interface Presentable

Returns:

a representation of the effective class of this object.

makePresentableInstance

public Presentable makePresentableInstance(Presentation presentation)
                                    throws PresentationException

Instance method to convert a Presentation into a Presentable. Ideally, this would be a class method, but such a method cannot be defined in an interface. Nor can it be defined in an abstract class with the intention of overriding it in a subclass. Polymorphism just doesn't work that way.
Therefore, the present value (as in fields) of the instance is essentially ignored - only the methods are important.

Specified by:

makePresentableInstance in interface Presentable

Parameters:

presentation - of a number to be converted into a Presentable number.

Returns:

a number in the form of a Presentable.

Throws:

PresentationException - if presentation cannot be parsed appropriately.

Parse

public static Presentable Parse(Presentation presentation)
                         throws PresentationException

Create a Rational from a Presentation and return it as a Presentable.

Parameters:

presentation - A presentation which should be parsed to form a Presentable.

Returns:

A Rational which corresponds to the presentation.

Throws:

PresentationException - if the presentation cannot be parsed as a Presentable object.

OpAnadic

private static Item OpAnadic(Operator op)
                      throws PresentableException

Throws:

PresentableException

OpMonadic

private static Item OpMonadic(Operator op,
                              Item number)
                       throws PresentableException

Throws:

PresentableException

OpDyadicNonComplex

private static Item OpDyadicNonComplex(Item current,
                                       Operator currentOp,
                                       BaseNumber number)
                                throws PresentableException

Note that the order of the operands is the reverse of the true order.

Parameters:

current - the "current" value - generally the accumulated result of the expression thus far.

currentOp - the "current" operator.

number - the new number to be combined with the current value

Returns:

the result of operating on current and number

Throws:

PresentableException

OpDyadicComplex

private static Item OpDyadicComplex(Item current,
                                    Operator currentOp,
                                    Item number)
                             throws PresentableException

Throws:

PresentableException

testExpression

protected static void testExpression(java.io.PrintStream out,
                                     SymbolicPresentation sp,
                                     java.lang.String label)

main

public static void main(java.lang.String[] args)

Main method for testing this class.

Parameters:

args - String[] : the command line options.

GetConstants

public static Lookupable GetConstants()

Returns:

Returns the $CONSTANTS.

SetConstants

public static void SetConstants(Lookupable constants)

Parameters:

constants - The Lookupable constants to be used as our "constants" definition to set.

See Also:

$CONSTANTS