Fixes a syntax error that prevented this example from being parsed.

Corrects some typos and fixes the stack command used to execute the examples.

Removes lots of code duplication

Just for completeness. The corresponding `max` implementations were already
there.

This means that `insert undefined bag` now evaluates to undefined in WHNF.

This was the intention all along.

This was a bug in the `delmin` helper that is used to delete the smallest
element of the right tree. It deleted too much.

This caused erroneous calls to rotateDoubleRight instead of rotateSingleRight,
thus disbalancing the tree and possibly failing to pattern match.

This is used in the Eq instance and also makes debugging and testing easier.

This is not strictly required by copar but allows for easier testing.

This returns the size of the tree, not the actual number of elements (there can
be more elements per node) and thus should not be in the public API.

This is a requirement for its use in copar and also allows for testing, since
`shouldBe` from hspec requires those two instances.

Due to the way the functor expression is parsed, this led to two nested
polynomial functors when functor rewriting is disabled. Without the parens we
get just one polynomial functor.

Alright, compromise. Word16 might have been a little too small

This should require 4 times less RAM and allow us to generate larger DFAs.

This allows to disable the 1-elem-block optimization to be able to compare the
running times with and with out it.

Queue.empty was being called with negative sizes