some ideas for the future:

- things specific to this repl:
	- saving & loading repl sessions somehow
	- collections of broadly useful functions that can be loaded into the repl
- optimization:
	- lazy evaluation
	- recognizing when reducing a term forms an endless loop and stopping reduction of that term
	- trampolining for reduction to prevent stack overflow
	- memoization
	- some more efficient way of storing & reducing functions based on finding expressions that occur in several parts of a program? probably related to the above