The line

notation `goldbach` := goldbach

in Preloaded causes a simple unfold goldbach / rw goldbach to fail. How might one work around this?

from_array should really be simply reduce(cls, reversed(arr), None), but it cannot, because None is interpreted as no initializer!

Evidently some tests are missing.

(This 'solution' does not check that the 'n' and 'B' occur at the same index.)

Tests fail on maximally polymorphic solutions, i.e. [a] -> [a] -> Bool.