com.rubecula.jep
Class TermEvaluator

java.lang.Object
  com.rubecula.jep.TermEvaluator

All Implemented Interfaces:

org.nfunk.jep.ParserVisitor

public class TermEvaluator

extends java.lang.Object

implements org.nfunk.jep.ParserVisitor

This class is part of the link from JQuantity to JEP - TermEvaluator depends on JEP, but there is no dependence on the com.rubecula.jquantity package. Instead this class depends on the com.rubecula.util package.

Since:

V_0_1

Version:

$Revision: 1.11 $

Author:

Robin Hillyard

Field Summary

private boolean	_Debug Debug flag.
private java.util.Hashtable	_DeclaredVariables JEP's internal store of declared variables.
private MillInterface	_Mill Mill to evaluate expressions.
private org.nfunk.jep.type.NumberFactory	_NumberFactory Number Factory to create numbers from the doubles which are generated by JEP when a constant is encountered.
private Lookupable	_UndeclaredVariables Store in which to lookup the current values of variables that arise in the terms of expressions.

Constructor Summary

(package private)

TermEvaluator(org.nfunk.jep.type.NumberFactory numberFactory, MillInterface mill, Lookupable variables) Constructor to create a new TermEvaluator for the purpose of evaluating expressions using JQuantity objects rather than Doubles.

Method Summary

Presentable	getValue() Mutating method to get the value of an expression (mutating because it pops the stack).
private Presentable	makePreciseNumber(java.lang.Object value)
private void	push(Presentable value)
void	setDebug(boolean debug)
void	setDeclaredVariables(java.util.Hashtable variables)
java.lang.Object	visit(org.nfunk.jep.ASTConstant node, java.lang.Object data) Method to visit a constant node.
java.lang.Object	visit(org.nfunk.jep.ASTFunNode node, java.lang.Object data) Method to visit a function node.
java.lang.Object	visit(org.nfunk.jep.ASTStart node, java.lang.Object data) Method to visit a start node.
java.lang.Object	visit(org.nfunk.jep.ASTVarNode node, java.lang.Object data) Method to visit a variable node.
java.lang.Object	visit(org.nfunk.jep.SimpleNode node, java.lang.Object data) Method to visit a simple node.

Methods inherited from class java.lang.Object

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

Field Detail

_Debug

private boolean _Debug

Debug flag. If true then values for nodes will be printed.

_NumberFactory

private final org.nfunk.jep.type.NumberFactory _NumberFactory

Number Factory to create numbers from the doubles which are generated by JEP when a constant is encountered.

_Mill

private final MillInterface _Mill

Mill to evaluate expressions.

_UndeclaredVariables

private final Lookupable _UndeclaredVariables

Store in which to lookup the current values of variables that arise in the terms of expressions.

_DeclaredVariables

private java.util.Hashtable _DeclaredVariables

JEP's internal store of declared variables.

Constructor Detail

TermEvaluator

TermEvaluator(org.nfunk.jep.type.NumberFactory numberFactory,
              MillInterface mill,
              Lookupable variables)
        throws MillException

Constructor to create a new TermEvaluator for the purpose of evaluating expressions using JQuantity objects rather than Doubles.

Parameters:

numberFactory - a number factory which produces objects which are Presentable and which are grist to the mill provided (basically this means that they should also be BaseNumbers).

mill - a computation mill which can will operate on the kinds of objects produced by the numberFactory (may be null, in which case an exception will be thrown when the reference is dereferenced).

variables - a lookupable map of variables (may be null).

Throws:

MillException

Method Detail

setDebug

public void setDebug(boolean debug)

setDeclaredVariables

public void setDeclaredVariables(java.util.Hashtable variables)

getValue

public Presentable getValue()

Mutating method to get the value of an expression (mutating because it pops the stack).

Returns:

the top value from the mill stack.

visit

public java.lang.Object visit(org.nfunk.jep.SimpleNode node,
                              java.lang.Object data)

Method to visit a simple node.

Specified by:

visit in interface org.nfunk.jep.ParserVisitor

Parameters:

node - a simple node.

data - the (generic) data passed in.

Returns:

the (generic) data passed out (the result of calling the childrenAccept method on the node, passing in this as the first argument).

visit

public java.lang.Object visit(org.nfunk.jep.ASTStart node,
                              java.lang.Object data)

Method to visit a start node.

Specified by:

visit in interface org.nfunk.jep.ParserVisitor

Parameters:

node - a start node.

data - the (generic) data passed in.

Returns:

the (generic) data passed out (the result of calling the childrenAccept method on the node, passing in this as the first argument).

visit

public java.lang.Object visit(org.nfunk.jep.ASTFunNode node,
                              java.lang.Object data)

Method to visit a function node. This method has the side effect of operating on the mill stack, where the operator is derived from calling getName() on the node.

Specified by:

visit in interface org.nfunk.jep.ParserVisitor

Parameters:

node - a function node.

data - the (generic) data passed in.

Returns:

the (generic) data passed out (the result of calling the childrenAccept method on the node, passing in this as the first argument).

visit

public java.lang.Object visit(org.nfunk.jep.ASTVarNode node,
                              java.lang.Object data)

Method to visit a variable node. If the _DeclaredVariables instance field is set, this method has the side effect of pushing the variable's value onto the mill stack, where the key for the variable is the result of calling getName() on the node.

Specified by:

visit in interface org.nfunk.jep.ParserVisitor

Parameters:

node - a variable node.

data - the (generic) data passed in.

Returns:

the (generic) data passed out (the result of calling the childrenAccept method on the node, passing in this as the first argument). // TODO Something weird going on here if we try to look for "declared" variables first - the JEP expression parser seems to magically pick up some declared variables (with 0 values) thus throwing off the calculations. Maybe investigate eventually.

visit

public java.lang.Object visit(org.nfunk.jep.ASTConstant node,
                              java.lang.Object data)

Method to visit a constant node. If the _NumberFactory instance field is set, this method has the side effect of pushing the constant's value onto the mill stack, where the pushed value is a Presentable. If _NumberFactory is unset, an exception will result, thus requiring the JEP expression parser to evaluate the expression as it would without JQuantity involvement.

Specified by:

visit in interface org.nfunk.jep.ParserVisitor

Parameters:

node - a constant node.

data - the (generic) data passed in.

Returns:

the (generic) data passed out (the result of calling the childrenAccept method on the node, passing in this as the first argument).

makePreciseNumber

private Presentable makePreciseNumber(java.lang.Object value)

push

private void push(Presentable value)