presnick/runestone — pull request #75 by aerenchyma (2014-09-18 16:26:45+00:00)
Title: add ps4 draft, sans unix problems

Unix problems + chapters not there yet, will be soon.

Could add more mechanical exercises, or other things, a bit more complexity with dictionaries? Haven't included the dictionary accumulation pattern in this problem set and was unsure of whether I should -- maybe ps5 is too late to introduce that and it should be seen here first?