Command Parser

• read a line
• split the line
• use first word in line to route to a particular API function, passing remaining words as arguments

Design Rule Discussion

• Rule of Modularity: Write simple parts connected by clean interfaces.
• Rule of Composition: Design programs to be connected with other programs.

• Rule of Representation: Fold knowledge into data, so program logic can be stupid and robust.

• What would we need to do if we wanted to handle more path directions (e.g. ‘northeast’, or ‘up’ and ‘down’?)
• There is redundant information in our data file: we must specify that Room A leads to Room B in the north and that Room B leads to Room A in the south. Is this a problem? If we wanted to be more DRY, what could we do?
• Could we follow a filter interface pattern like bc (implement an interactive mode and a batch mode)

More Complex Parsing

What if you wanted to handle commands such as

> throw ball at window
> fight monster with magic sward
> drop 5 candles

• regular expressions
• flex/bison (and Python’s C bindings)