Resulting design of useful data types for "Simple"
Simple types: numbers, characters, boolean, symbol
Compound types: lists, "code objects"

Discussion notes: They latched onto the similarities to Scheme pretty early on,
with one student arguing for the inclusion of symbols as a simple type before
even understanding why Scheme uses them. As discussion continued, they felt
that symbols were an appropriate way to refer to fragments of code and although
they acknowledged that "code objects" could probably be implemented using lists
and symbols, they were more comfortable considering "code objects" to be their
own type.

When it came time to eliminating redundant types and generalizing as much as
possible, they remarked that booleans should be a type in their own right but
whatever implementation they use, they'd better allow a boolean value to be
compared to a number. Multiple students reinforced this decision, citing
frustration with languages that don't allow them to do this. :)