🚀 go-pugleaf

Sterling and Shapiro give the following procedure for copying:

copy(X,Y):- assert('$foo'(X)),retract('$foo'(Y)).

I have found the following to be much faster:

copy(X,Y):- findall(Z, Z = X,[Y]).

This only works with findall not setof or bagof. Can anyone
explain why this works? In general, I have discovered, destructive
variable bindings embedded within findall have no global effect.
Again this is not the case with setof and bagof. Very peculiar
isn't it?
                          --- Dale Gerdemann