Package com.singularsys.jep.misc.overloadedfunctions

Class AlternateFunctions

java.lang.Object
com.singularsys.jep.functions.PostfixMathCommand
com.singularsys.jep.misc.overloadedfunctions.AlternateFunctions
All Implemented Interfaces:
CallbackEvaluationI, JepComponent, PostfixMathCommandI, Serializable
public class AlternateFunctions extends PostfixMathCommand implements CallbackEvaluationI, JepComponent
Allows function to be overloaded with multiple candidate functions chosen by the number of arguments.

For example the atan function can be overloaded so that it has a one argument and two argument version. 


    UnaryFunction uf = new ArcTangent();
    BinaryFunction bf =new ArcTangent2();
    AlternateFunctions af = new AlternateFunctions(uf, bf);
    jep.addFunction("atan",af);
    jep.reinitializeComponents();
    Node node = jep.parse("atan(1)");
    Object res = jep.evaluate(node);
    assertEquals(Math.PI/4,(double) res,1e-9);
    Node node2 = jep.parse("atan(1,2)");
    Object res2 = jep.evaluate(node2);
    assertEquals(Math.atan2(1,2),(double) res2,1e-9);

The above resolution happens at evaluation time. If the AlternateFunctionGrammerMatcher is used then resolution happens at parse time.

Evaluation of overloaded functions is done by creating a temporary node with the appropriate function and evaluating this node. This means any type of function can be used, including those that implement CallbackEvaluationI.

Since:
Jep 4.1
See Also:

  • Field Details

  • Constructor Details

    • AlternateFunctions

      public AlternateFunctions(PostfixMathCommandI... functions)
      Constructor. Any type of function can be used, including those that implement CallbackEvaluationI.
      Parameters:
      functions - the list of function

  • Method Details

    • checkNumberOfParameters

      public boolean checkNumberOfParameters(int n)
      Description copied from class: PostfixMathCommand
      Checks the number of parameters of the function. Functions which set numberOfParameter=-1 should overload this method
      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.

    • getFunctionForNArgs

      public PostfixMathCommandI getFunctionForNArgs(int n)
      Returns the function that matches the number of arguments.
      Parameters:
      n - the number of arguments
      Returns:
      the function that matches the number of arguments or null if none found.

    • init

      public void init(Jep jep)
      Description copied from interface: JepComponent
      Initialize the component. This method 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 a new instance, null or 'this'.

    • 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:

    • getDescription

      public String getDescription()
      Description copied from class: PostfixMathCommand
      Return a description of the function from the properties file. The property name is the class name followed by ".description". The property is found using the JepMessages class, which can be configured to add additional properties files. If PostfixMathCommand.setDescription(String) has been called, return the description set by that method instead.
      Specified by:
      getDescription in interface PostfixMathCommandI
      Overrides:
      getDescription in class PostfixMathCommand
      Returns:
      the description of the function