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++)