Implemented "Modify Word Length"

Closes #29 (closed)

Port.InputPort has a new property value_length that describes the word length of the input on the operation related to that port.

Port.InputPort.signal and its abstract function has been removed according to the class diagram.01_-Swords_and_Sandals_Classic_Collection-_Title_Theme

b_asic/port.py

@@ -35,15 +35,6 @@ class Port(ABC):
         """Return a list of all connected signals."""
         raise NotImplementedError
 
-    @abstractmethod
-    def signal(self, i: int = 0) -> Signal:
-        """Return the connected signal at index i.
-
-        Keyword argumens:
-        i: integer index of the signal requsted.
-        """
-        raise NotImplementedError
-
     @property
     @abstractmethod
     def connected_ports(self) -> List["Port"]:
@@ -58,20 +49,23 @@ class Port(ABC):
     @abstractmethod
     def connect(self, port: "Port") -> Signal:
         """Create and return a signal that is connected to this port and the entered
-        port and connect this port to the signal and the entered port to the signal."""
+        port and connect this port to the signal and the entered port to the signal.
+        """
         raise NotImplementedError
 
     @abstractmethod
     def add_signal(self, signal: Signal) -> None:
         """Connect this port to the entered signal. If the entered signal isn't connected to
-        this port then connect the entered signal to the port aswell."""
+        this port then connect the entered signal to the port aswell.
+        """
         raise NotImplementedError
 
     @abstractmethod
     def disconnect(self, port: "Port") -> None:
         """Disconnect the entered port from the port by removing it from the ports signal.
         If the entered port is still connected to this ports signal then disconnect the entered
-        port from the signal aswell."""
+        port from the signal aswell.
+        """
         raise NotImplementedError
 
     @abstractmethod
@@ -119,31 +113,38 @@ class InputPort(AbstractPort):
     """
 
     _source_signal: Optional[Signal]
+    _value_length: Optional[int]
 
     def __init__(self, port_id: PortIndex, operation: Operation):
         super().__init__(port_id, operation)
         self._source_signal = None
+        self._value_length = None
 
     @property
     def signals(self) -> List[Signal]:
         return [] if self._source_signal is None else [self._source_signal]
 
-    def signal(self, i: int = 0) -> Signal:
-        assert 0 <= i < self.signal_count(), "Signal index out of bound."
-        assert self._source_signal is not None, "No Signal connect to InputPort."
-        return self._source_signal
+    @property
+    def value_length(self) -> Optional[int]:
+        return self._value_length
 
     @property
     def connected_ports(self) -> List[Port]:
         return [] if self._source_signal is None or self._source_signal.source is None \
             else [self._source_signal.source]
 
+    @value_length.setter
+    def value_length(self, bits: Optional[int]) -> None:
+        assert (isinstance(bits, int) and bits >= 0) or bits is None, \
+            "Value length on input port has to be a non-negative integer or None."
+        self._value_length = bits
+
     def signal_count(self) -> int:
         return 0 if self._source_signal is None else 1
 
     def connect(self, port: "OutputPort") -> Signal:
         assert self._source_signal is None, "Connecting new port to already connected input port."
-        return Signal(port, self)        # self._source_signal is set by the signal constructor
+        return Signal(port, self)        # self._source_signal is set by the signal constructor.
 
     def add_signal(self, signal: Signal) -> None:
         assert self._source_signal is None, "Connecting new port to already connected input port."
@@ -160,12 +161,13 @@ class InputPort(AbstractPort):
         old_signal: Signal = self._source_signal
         self._source_signal = None
         if self is old_signal.destination:
-            # Disconnect the dest of the signal if this inputport currently is the dest
+            # Disconnect the dest of the signal if this inputport currently is the dest.
             old_signal.remove_destination()
 
     def clear(self) -> None:
         self.remove_signal(self._source_signal)
 
+
 class OutputPort(AbstractPort):
     """Output port.
     TODO: More info.
@@ -194,14 +196,14 @@ class OutputPort(AbstractPort):
         return len(self._destination_signals)
 
     def connect(self, port: InputPort) -> Signal:
-        return Signal(self, port)      # Signal is added to self._destination_signals in signal constructor
+        return Signal(self, port)  # Signal is added to self._destination_signals in signal constructor.
 
     def add_signal(self, signal: Signal) -> None:
         assert signal not in self.signals, \
                 "Attempting to connect to Signal already connected."
         self._destination_signals.append(signal)
         if self is not signal.source:
-            # Connect this outputport to the signal if it isn't already
+            # Connect this outputport to the signal if it isn't already.
             signal.set_source(self)
 
     def disconnect(self, port: InputPort) -> None: