com.singularsys.jep.functions
Class If

java.lang.Object
  com.singularsys.jep.functions.PostfixMathCommand
      com.singularsys.jep.functions.If

All Implemented Interfaces:

CallbackEvaluationI, PostfixMathCommandI, java.io.Serializable

public class If
extends PostfixMathCommand
implements CallbackEvaluationI

The if(condExpr, posExpr, negExpr) function. The value of trueExpr will be returned if condExpr is >0 or Boolean.TRUE and value of negExpr will be returned if condExpr is <= 0 or Boolean.TRUE.

This function performs lazy evaluation so that only posExpr or negExpr will be evaluated. For Complex numbers only the real part is used.

An alternate form if(condExpr, posExpr, negExpr, zeroExpr) is also available. Note most computations are carried out over floating point doubles so testing for zero can be dangerous.

This function implements the SpecialEvaluationI interface so that it handles setting the value of a variable.

Since:

Feb 05 Handles Number arguments, so works with Integers rather than just Doubles

Version:

2.3.0 beta 1 now supports a Boolean first argument.

Author:

Rich Morris Created on 18-Nov-2003

See Also:

Serialized Form

Field Summary

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

curNumberOfParameters, numberOfParameters

Constructor Summary

If()

Method Summary

boolean	checkNumberOfParameters(int n) Checks the number of parameters of the call.
java.lang.Object	evaluate(Node node, Evaluator pv) Performs some special evaluation on the node.
void	run(java.util.Stack<java.lang.Object> aStack) Run the function on the stack.

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

checkStack, getNumberOfParameters, setCurNumberOfParameters

Methods inherited from class java.lang.Object

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

Constructor Detail

If

public If()

Method Detail

checkNumberOfParameters

public boolean checkNumberOfParameters(int n)

Checks the number of parameters of the call.

Specified by:

checkNumberOfParameters in interface PostfixMathCommandI

Overrides:

checkNumberOfParameters in class PostfixMathCommand

Parameters:

n - number of parameters function will be called with.

Returns:

false if an illegal number of parameters is supplied, true otherwise.

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

Throws:

EvaluationException

See Also:

Evaluator

run

public void run(java.util.Stack<java.lang.Object> aStack)
         throws EvaluationException

Description copied from interface: PostfixMathCommandI

Run the function on the stack. Pops the arguments from the stack, and pushes the result on the top of the stack.

Specified by:

run in interface PostfixMathCommandI

Throws:

EvaluationException