Poplog is a logic based programming language and it is multi-language programming environment for the programming languages POP-11, Common Lisp, Prolog and standard ML. It was developed in UK for teaching and research in artificial intelligence at the University of Sussex. It is free Cross-platform Compiler.
The given example is consist of two parts in which first part will store the file as fact.pl and placed in working folder of poplog and then the second part have to enter manually. [-fact].
% fact.pl fact(X, F) :- ( X=0, F=1; Y is X-1, fact(Y, Z), F is X*Z), write(X), write('! = '), write(F), nl. % interactive [-fact]. fact(16,X).