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 depen-
       dencies between any number of state variables, but a  com-
       ponent 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 opera-
              tions  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 cor-
              responding  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  opera-
              tion.   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 instantia-
              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++)