Package com.singularsys.extensions.xjep

Class Preprocess

java.lang.Object

com.singularsys.jep.functions.PostfixMathCommand

com.singularsys.extensions.xjep.Preprocess

All Implemented Interfaces:

CallbackEvaluationI, JepComponent, PostfixMathCommandI, java.io.Serializable

public class Preprocess
extends PostfixMathCommand
implements JepComponent, CallbackEvaluationI

Runs the preprocessors on an expression during evaluation. This can be used to perform symbolic operations during evaluation.

 expr:=0;
 for(n=1;n<=4;++n) { preprocess(expr:=eqn(expr)+x^eval(n)); }
 

The for loop from the com.singularsys.extensions.structure package repeatedly evaluates the block. To perform symbolic operations we use the Preprocess function. This in turn uses a symbolic assignment operation XAssign, extracts the current expression for the expr variable using the ExtractEqn function, and evaluates the value of n using the Eval function. evaluate

Since:

Jep 4.0/Extension 2.1

See Also:

Eval, Serialized Form

Field Summary

Fields inherited from class com.singularsys.jep.functions.PostfixMathCommand

curNumberOfParameters, name, NaN, numberOfParameters

Constructor Summary

Constructors

Constructor	Description
Preprocess()
Preprocess(XJep xj)

Method Summary

Modifier and Type	Method	Description
java.lang.Object	evaluate(Node node, Evaluator pv)	Performs some special evaluation on the node.
JepComponent	getLightWeightInstance()	Gets a light-weight instance suitable for using in multiple threads.
void	init(Jep jep)	Initialize the component.

Methods inherited from class com.singularsys.jep.functions.PostfixMathCommand

asArray, asBool, asDouble, asInt, asLong, asStrictInt, asString, checkNumberOfParameters, getName, getNumberOfParameters, run, setCurNumberOfParameters, setName, toString, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

Preprocess

public Preprocess()

Preprocess

public Preprocess(XJep xj)

Method Detail

evaluate

public java.lang.Object evaluate(Node node,
                                 Evaluator pv)
                          throws EvaluationException

Description copied from interface: CallbackEvaluationI

Performs some special evaluation on the node. This method has the responsibility for evaluating the children of the node and it should generally call

 pv.eval(node.jjtGetChild(i))   
 

for each child. The SymbolTable is not passed as an argument. This is because it is better practice to get and set variable values by using node.getVar().setValue() rather that through the SymbolTable with requires a hashtable lookup.

Specified by:

evaluate in interface CallbackEvaluationI

Parameters:

node - The current node

pv - The visitor, can be used evaluate the children

Returns:

the value after evaluation. This value will be passed to other functions higher up the node tree. The value can be any type including Double or Vector<Object>

Throws:

EvaluationException - if the calculation cannot be performed

See Also:

Evaluator

init

public void init(Jep jep)

Description copied from interface: JepComponent

Initialize the component. This methods is called whenever a component is added to Jep. Hence it allows components to keep track of the other components they may rely on.

Specified by:

init in interface JepComponent

Parameters:

jep - the current Jep instance

getLightWeightInstance

public JepComponent getLightWeightInstance()

Description copied from interface: JepComponent

Gets a light-weight instance suitable for using in multiple threads.

Specified by:

getLightWeightInstance in interface JepComponent

Returns:

either an new instance, null or 'this'.