Koka-inspired local mutable variables for cleaner comprehensions

The new proposal is here: Local accumulators for cleaner comprehensions.

Click here if you want to jump directly to the new part of the proposal.

Everyone is welcome to post your opinions and feedback on the new thread, even if the new proposal does not really change the opinion you posted here.

I will close this thread. @hst337 (and anyone else), alternative answers to the problem statement with Pathex, Iteraptor, or anything else is very welcome in the new thread.