No Exercise Today
May 20, 2016
I’ve been busy at work and haven’t had time to prepare an exercise for today. I apologize.
Your task is to solve a previous exercise that you haven’t yet solved. Have fun!
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Programming Praxis 
A take on that interleaved sorting exercise: a minimal way to see even and odd positions as collections of their own right, backed by the actual store that contains them both. (This is Python.)
class See(object): def __init__(self, store, length, index): self.store = store self.length = length self.index = index def __setitem__(self, x, vs): '''handle self[:] = vs when lengths match''' for k, o in enumerate(vs): self.store[self.index(k)] = o def __iter__(self): for k in range(self.length): yield self.store[self.index(k)] def demonstrate(data): every = See(data, len(data), lambda k: k) even = See(data, -(-len(data) // 2), lambda k: 2 * k) odd = See(data, len(data) // 2, lambda k: 2 * k + 1) print('before:', *map(''.join, (every, even, odd))) even[:] = sorted(even) odd[:] = sorted(odd, reverse = True) print('after:', *map(''.join, (every, even, odd))) demonstrate(list('abracadabra')) demonstrate(list('0123456789')) # before: abracadabra arcdba baaar # after: arabbacadar aabcdr rbaaa # before: 0123456789 02468 13579 # after: 0927456381 02468 97531