Package com.singularsys.jep.misc.overloadedfunctions

Class OverloadedFunctionByStructure

java.lang.Object
com.singularsys.jep.functions.PostfixMathCommand
com.singularsys.jep.misc.overloadedfunctions.OverloadedFunctionByStructure
All Implemented Interfaces:
CallbackEvaluationI, JepComponent, PostfixMathCommandI, Serializable
public class OverloadedFunctionByStructure extends PostfixMathCommand implements CallbackEvaluationI, JepComponent
Allows function to be overloaded with two candidate functions and a predicate that tests the structure of the parse tree to see which function should be applied.

For example in the extensions package the dot operator can be overloaded with a custom function ChainingOpPfmc that allows a method chaining syntax so a syntax like [1..10] . map(x->x^2). This is used when the second argument is a ChainedFunctionI. Otherwise the regular dot product function is used. 

  Operator dot_op = jep.getOperatorTable().getDot();
  dot_op.setPFMC(new OverloadedFunctionByStructure(
          new ChainingOpPfmc(),
          new Dot(), 
          n -> n.jjtGetChild(1).getPFMC() instanceof ChainedFunctionI));
  jep.reinitializeComponents();

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

    • OverloadedFunctionByStructure

      public OverloadedFunctionByStructure(PostfixMathCommandI function1, PostfixMathCommandI function2, Predicate<Node> argTest)
      Constructor. Any type of function can be used, including those that implement CallbackEvaluationI.
      Parameters:
      function1 - the first function
      function2 - the second function
      argTest - a predicate that tests the structure of the parse tree, the first function is used if this returns true.

  • 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.

    • getNumberOfParameters

      public int getNumberOfParameters()
      Calculates the possible number of parameters. If both functions have the same number of parameters then return than, otherwise return -1.
      Specified by:
      getNumberOfParameters in interface PostfixMathCommandI
      Overrides:
      getNumberOfParameters in class PostfixMathCommand
      Returns:
      the possible number of parameters

    • 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:

    • getFunctionFor

      public PostfixMathCommandI getFunctionFor(Node node)
      Get the actual function that will be used for a given node.
      Parameters:
      node - the node to test
      Returns:
      either function1 or function2 depending on the test

    • 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'.

    • getFunction1

      public PostfixMathCommandI getFunction1()

    • getFunction2

      public PostfixMathCommandI getFunction2()

    • getPredicate

      public Predicate<Node> getPredicate()

    • 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