ex 5.23 - let-exp expansion
ex 5.23 - remove some comments
ex 5.23 - refactor (quasiquote)
ex 5.23 - setup transformers
ec - provide evalator without comments
ex 5.23 - modify evaluator
ex 5.23 - not working no clue
ex 5.23 - working test cases for cond
ex 5.23 - handling named let
ex 5.23 - expand "define"
ec - TODO done
ex 5.23 - looks better using quasiquotes
ex 5.23 - done
ex 5.23 - rename files

as the "common" is supposed to export those
that might be used by other modules,
not those that modifies the machine
ex 5.24 - building blocks
5.24 - kind of confusing
ec - some convention are needed
ex 5.24 - yet again not satisfied with the design
ex 5.24 - just some trivial progress ..
Problem 80 - reworked a little bit