Initial addition of Python scripts

letter.py

@@ -0,0 +1,48 @@
+from workspaceObject import WorkspaceObject
+from slipnet import slipnet
+
+class Letter(WorkspaceObject):
+	def __init__(self,string,position,length):
+		WorkspaceObject.__init__(self,string)
+		from workspace import workspace
+		workspace.objects += [ self ]
+		string.objects += [self ]
+		self.leftStringPosition = position
+		self.leftmost = self.leftStringPosition == 1
+		self.rightStringPosition = position
+		self.rightmost = self.rightStringPosition == length
+
+	def describe(self,position,length):
+		if length == 1:
+			self.addDescription(slipnet.stringPositionCategory,slipnet.single)
+		if self.leftmost and length > 1: # ? why check length ?
+			self.addDescription(slipnet.stringPositionCategory,slipnet.leftmost)
+		if self.rightmost and length > 1: # ? why check length ?
+			self.addDescription(slipnet.stringPositionCategory,slipnet.rightmost)
+		if length > 2 and position * 2 == length + 1:
+			self.addDescription(slipnet.stringPositionCategory,slipnet.middle)
+
+	def __repr__(self):
+		return '<Letter: %s>' % self.__str__()
+
+	def __str__(self):
+		if not self.string:
+			return ''
+		i = self.leftStringPosition - 1
+		if len(self.string) <= i:
+			raise ValueError, 'len(self.string) <= self.leftStringPosition :: %d <= %d' % (len(self.string),self.leftStringPosition)
+		return self.string[ i ]
+
+	def distinguishingDescriptor(self,descriptor):
+		"""Whether no other object of the same type (letter) has the same descriptor"""
+		if not WorkspaceObject.distinguishingDescriptor(self,descriptor):
+			return False
+		for objekt in self.string.objects:
+			# check to see if they are of the same type
+			if isinstance(objekt,Letter) and objekt != self:
+				# check all descriptions for the descriptor
+				for description in objekt.descriptions:
+					if description.descriptor == descriptor:
+						return False
+		return True
+