Exercise 2.44: the first of a huge set of unrunnable code? check with community.schemewiki.org/?sicp-solutions
Exercise 2.45 - builds a bit on 2.44
Exercise 2.46: vectors. Generalized code is actually CLEANER, because it made me realize I could just use (map) and be done in a couple lines.
Exercise 2.47: 2 different low-level implementations of frames. this might be more instructive if we could actually RUN the code meaningfully and see that the 2 forms both work
Exercise 2.48: segments from vectors. just as easy as vectors themselves!?
Exercise 2.49 - applying a painting system that we can't run
Exercise 2.50 - practice with the (transform-painter) api
Exercise 2.51 - (below), by analogy with (beside). monkey see monkey do