99 Bottles of Beer/Prolog

99 Bottles of Beer done in Prolog-languages

Prolog

Works with: SWI Prolog

<lang prolog>bottles(0). bottles(X):-

   writef('%t bottles of beer on the wall \n',[X]),
   writef('%t bottles of beer\n',[X]),
   write('Take one down, pass it around\n'),
   succ(XN,X),
   writef('%t bottles of beer on the wall \n\n',[XN]),
   bottles(XN).

- bottles(99).</lang>

It is possible to extend the previous version so to handle singular and plurals of the word 'bottle':

<lang prolog>bottles(0):- write('no more bottles of beer'). bottles(B) :-

   dif(B,0), NewB is B - 1,
   (
       dif(B,1), writef('%t bottles of beer on the wall \n',[B]), writef('%t bottles of beer\n',[B]);
       writef('%t bottle of beer on the wall \n',[B]), writef('%t bottle of beer\n',[B])
   ),
   write('Take one down, pass it around\n'),
   (
       NewB > 1, writef('%t bottles of beer on the wall \n\n',[NewB]);
       NewB =:= 1, writef('%t bottle of beer on the wall \n\n',[NewB]); 
       true
   ), 
   bottles(NewB).

- bottles(99).</lang>

Another version that handles plural/not plural conditions.

<lang prolog>line1(X):- line2(X),write(' on the wall'). line2(0):- write('no more bottles of beer'). line2(1):- write('1 bottle of beer'). line2(X):- writef('%t bottles of beer',[X]). line3(1):- write('Take it down, pass it around'). line3(X):- write('Take one down, pass it around'). line4(X):- line1(X).

bottles(0):-!. bottles(X):-

   succ(XN,X),
   line1(X),nl,
   line2(X),nl,
   line3(X),nl,
   line4(XN),nl,nl,
   !,
   bottles(XN).

- bottles(99).</lang>

Visual Prolog

<lang visual prolog> implement main

   open core, std, console

class predicates

   bottles : (integer) -> string procedure (i).

clauses

   bottles(1) = "bottle" :- !.
   bottles(_) = "bottles".

   run():-
       init(),
       foreach B = downTo(99,1) do
           write(B," ",bottles(B), " of beer on the wall,\n"),
           write(B," ",bottles(B), " of beer,\n"),
           write("Take one down, pass it around,\n"),
           write(B-1," ",bottles(B-1)," of beer on the wall.\n\n")
       end foreach,

       succeed().

end implement main

goal

   mainExe::run(main::run).

</lang>