There are two candidates for a visiting math position coming next week. They will be speaking on Monday night and Wednesday night. I think that the department will be providing Pizza. I'll offer the added incentive that anyone who comes to a talk and sends the department a summary of your reactions to the candidate gets one point of extra credit in the class. This helps us distinguish the roles of a number of things.
L is used for locations.
An environment maps each identifier to a location Surprisingly, it seems that every identifier has a location. A closer reading of the semantics suggests that undefined may be used. It appears that the boolean is used to indicate whether or not the location is allocated. Each has an additional boolean flag. Continuations are used.