Prolog. No command line interface yet

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+% Synopsis:
+% # gplc gcd.pro
+% # ./gcd
+% | ?- gcd2(22, 121, 11).
+% | ?- gcd2(22, 121, X).
+% | ?- gcdn([22, 33], 11).
+% | ?- gcdn([22, 33, 44], 11).
+% | ?- gcdn([22], 11).      
+% | ?- gcdn([22, 33, 44], B). 
+
+
+% 1st number, 2nd number, GCD
+
+% It is true that GCD of A and 0 is A
+% (The fact is GCD of A and 0 is A)
+gcd2(A, 0, A).
+
+% It is true that G is GCD of A and B
+% when A>0 and B>0 and G is GCD of B and A % B
+gcd2(A, B, G) :- A>0, B>0, N is mod(A, B), gcd2(B, N, G).
+
+gcdn(A, [], A).
+gcdn(A, [B|Bs], G) :- gcd2(A, B, N), gcdn(N, Bs, G).
+gcdn([A|As], G) :- gcdn(A, As, G).
+
+% http://www.gprolog.org/manual/html_node/gprolog008.html#toc9
+%:- initialization(main).
+
+
+% http://www.fraber.de/bap/bap76.html
+%main :-
+%    argument_list(Args),
+%    gcdn(Numbers, G),
+%    write(G), nl.
+