…fyWithSet protocol left as stub for the brave ones.
This issue does not affect external correctness but will adversely affect performance in the presence of duplicated facts.
…*fd support for eqfd sugar. add send more money fd version using eqfd sugar. still suprisingl slow, seems like perhaps too much work is being done on the intermediate vars.
…pdate cryptarithfd bench
…false in to-stream
…lse on failed unification, it returns nil.