Package com.singularsys.jep.functions

Class If

java.lang.Object
com.singularsys.jep.functions.PostfixMathCommand
com.singularsys.jep.functions.If
All Implemented Interfaces:
CallbackEvaluationI, PostfixMathCommandI, Serializable
Direct Known Subclasses:
NullWrappedIf
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. If condExpr is NaN then NaN is returned.

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.

Note most computations are carried out over floating point doubles so testing for zero can be dangerous.

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:

  • Field Details

    • falseValue

      protected Object falseValue

  • Constructor Details

    • If

      public If()

    • If

      public If(Object falseValue)
      If this constructor is used then a two argument version can be used if(condExpr, posExpr) is also available.
      Parameters:
      falseValue - the value to return when condExpr is false in the two argument version

  • Method Details

    • 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 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:

    • getFalseValue

      public Object getFalseValue()
      The value returned for false values in the two argument version.
      Returns:
      value returned
      Since:
      3.4.0