- Nobody does `import random` anymore.
- Random numbers are gotten from `ctx.random`, which is an object
of type `Randomness` with all the convenience methods that used to
be obnoxious functions in the `formulas` module.
- Every place that was using `random.random()` to implement the
equivalent of Python3 `random.choices(seq, weights)` has been updated
to use `ctx.random.weighted_choice(seq, weights)`.
This has a functional effect, since the details of random number
generation have changed. The *statistical* effect should be small.
I do observe that Copycat is having trouble inventing the "mrrjjjj"
solution right now (even in 1000 test runs), so maybe something is
slightly broken.
Without this patch, `python main.py abc aabbcc milk` will reliably crash.
I believe what happens here is that we initialize all the slipnodes and
everything, and then `slipnet.predecessor` becomes `None`, which means
that if that concept ever arises on its own (vs. arising as the "opposite"
of "successor"), we'll be passing around `None` instead of a proper `Slipnode`
and everything goes sideways.
This line doesn't correspond obviously to anything in the Java code,
so I think it's just bogus --- an experiment in "brain damage" that was
accidentally committed?
