Pairs.
Pairs are reducible.
Name block parameters.
Count least fixed point iterations under DEBUG.
Pair equality is by receiver properties first.
Pair hashing.
Singleton null pair instance.
Construct (nil, nil) → [HMRPair null].
Pairs are appendable.
Parse trees are made from cons cells.

Oh look, the associativity and all makes sense now!
Don’t compact concatenations of null prefixes.

At least, not this way.
Another named block parameter.
Compact concatenations involving null parses.

Per the paper. Wish I’d read this straight away.
Correct the alternation compaction tests.
Reduce null parses at compaction.
Merge pull request #67 from robrix/reduction-compactions

Reduction compactions