org.nfunk.jep.function.If Maven / Gradle / Ivy
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/* @author rich
* Created on 18-Nov-2003
*/
package org.nfunk.jep.function;
import org.nfunk.jep.*;
import org.nfunk.jep.type.*;
/**
* 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.
* @author Rich Morris
* Created on 18-Nov-2003
* @version 2.3.0 beta 1 now supports a Boolean first argument.
* @since Feb 05 Handles Number arguments, so works with Integers rather than just Doubles
*/
public class If extends PostfixMathCommand implements CallbackEvaluationI {
/**
*
*/
public If() {
super();
numberOfParameters = -1;
}
/*
* Performs the specified action on an expression tree.
* Serves no function in standard JEP but
* @param node top node of the tree
* @param pv The visitor, can be used evaluate the children.
* @return top node of the results.
* @throws ParseException
public Node process(Node node,Object data,ParserVisitor pv) throws ParseException
{
return null;
}
*/
/**
* Checks the number of parameters of the call.
*
*/
public boolean checkNumberOfParameters(int n) {
return (n == 3 || n == 4);
}
/**
*
*/
public Object evaluate(Node node,EvaluatorI pv) throws ParseException
{
int num = node.jjtGetNumChildren();
if( !checkNumberOfParameters(num))
throw new ParseException("If operator must have 3 or 4 arguments.");
// get value of argument
Object condVal = pv.eval(node.jjtGetChild(0));
// convert to double
double val;
if(condVal instanceof Boolean)
{
if(((Boolean) condVal).booleanValue())
return pv.eval(node.jjtGetChild(1));
return pv.eval(node.jjtGetChild(2));
}
else if(condVal instanceof Complex)
val = ((Complex) condVal).re();
else if(condVal instanceof Number)
val = ((Number) condVal).doubleValue();
else
throw new ParseException("Condition in if operator must be double or complex");
if(val>0.0)
return pv.eval(node.jjtGetChild(1));
else if(num ==3 || val <0.0)
return pv.eval(node.jjtGetChild(2));
return pv.eval(node.jjtGetChild(3));
}
}