99 Bottles of Beer/Prolog: Difference between revisions
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{{collection|99 Bottles of Beer}}
[[99 Bottles of Beer]] done in Prolog-languages
__toc__
===Prolog===
{{works with|SWI Prolog}}
<syntaxhighlight 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).</syntaxhighlight>
It is possible to extend the previous version so to handle singular and plurals of the word 'bottle':
<syntaxhighlight 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).</syntaxhighlight>
Another version that handles plural/not plural conditions.
<syntaxhighlight 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).</syntaxhighlight>
===Visual Prolog===
<syntaxhighlight 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).</syntaxhighlight>
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