TransferFunct(3U)					    InterViews Reference Manual 					 TransferFunct(3U)

NAME

       TransferFunct - transfer function base class

SYNOPSIS

       #include <Unidraw/transfn.h>

DESCRIPTION

       A  transfer  function  defines relationships between state variables.  A component uses a transfer function to enforce dependencies between
       its state variables during dataflow. State variables whose values change as a result of data flowing into the component can thus affect the
       component's  dependent state variables as defined by its transfer function.  A transfer function can define dependencies between any number
       of state variables, but a component can define only one transfer function.

PUBLIC OPERATIONS

       virtual void Evaluate(Path* = nil)
	      Enforce the transfer function's dependencies between its state variables, optionally depending on the information in a  path.   This
	      operation does nothing by default.

       virtual TransferFunct* Copy()
	      Return a copy of the transfer function.  Subclasses redefine this operation to return an instance of their type.

       virtual void Read(istream&)
       virtual void Write(ostream&)
	      Read  and write the transfer function's contents to a stream to support catalog operations.  Read and write typically call first the
	      corresponding operations defined by their parent class, and then they read or write their class-specific state.

       virtual ClassId GetClassId()
       virtual boolean IsA(ClassId)
	      GetClassId returns the unique class identifier for the TransferFunct subclass, while IsA returns whether the instance is of a  class
	      or subclass corresponding to the given identifier.  IsA typically checks the given identifier against the instance's own (as defined
	      by its GetClassId operation) and, failing that, calls its parent classes' IsA operation.	All subclasses	must  redefine	GetClassId
	      and IsA to ensure that their identifiers are unique and that instances are written and read properly.

PROTECTED OPERATIONS

       TransferFunct()
	      The constructor is protected to prevent instantiation.

       virtual Connector* GetBinding(StateVar*)
	      Return the connector to which a state variable is bound.

SEE ALSO

       Catalog(3U), Component(3U), Connector(3U), Creator(3U), Path(3U), StateVar(3U) classes(3U), istream(3C++), ostream(3C++)

Unidraw 							   6 August 1990						 TransferFunct(3U)