It turns out that the binary_number relation is used in such a way that it needs to be able to backtrack to preprend leading zeros to the list of bits it constructs to automatically build bitfields of a given width (with the collect//2 DCG.)
Allow for "compilation" of new func/3 rules.
Add comment of crude grammar for Joy syntax.
Minor rearrangements.
show_joy_compile uses portray_clause/1.