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transfns(3U) InterViews Reference Manual transfns(3U)

TF_2Port, TF_Direct - transfer function subclasses

#include <Unidraw/transfns.h>

The TransferFunct abstract base class defines the transfer function protocol. The library predefines two subclasses. TF_2Port is a subclass that acts as an abstract base class for transfer functions having two sets of state variables, ``input'' and ``output'', with output variables always dependent on input variables. TF_Direct is a subclass of TF_2Port that defines a one-to-one assignment relationship between an input and an output state variable.

Evaluate first carries out information transfer between dependent state variables by calling the Transfer operation (described below). Then it iterates through its output state variables; those that have changed (according to the ChangedOutput operation, described below) get Transmit called on the connector they're bound to. Subclasses needn't redefine this operation if they implement Transfer and ChangedOutput appropriately.
Retrieve and assign the TF_2Port's input and output state variables, identified serially. These operations do nothing by default; subclasses must allocate the storage they require.
Return the number of input and output state variables. These operations return zero by default.

The constructor is protected to prevent instantiation.
Enforce the subclass-specific dependencies between the TF_2Port's state variables. This operation does nothing by default.
Return whether the output state variable with the given index has changed its value since the last call to Transfer. Subclasses redefine this operation according to the semantics of their Transfer operation.

Instantiate a new object, optionally specifying the input state variable and its dependent output state variable.
Retrieve and assign the TF_Direct's input and output state variables. Specifying an index greater than zero does nothing, since TF_Direct defines a dependency between one input and one output state variable.
Return the number of input and output state variables. These operations return zero by default.
These operations return 1.

Assign the input state variable to the output state variable, setting a flag indicating that the output value has changed.
Return the status of the flag set by Transfer. The flag is reset as a side-effect of this operation.

TransferFunct(3U)

6 August 1990 Unidraw