109 lines
2.4 KiB
Perl
109 lines
2.4 KiB
Perl
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% ----------------------------------------------------------------------
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% The Computer Language Benchmarks Game
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% http://shootout.alioth.debian.org/
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% Contributed by Anthony Borla
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% Modified by Glendon Holst
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% ----------------------------------------------------------------------
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:- yap_flag(unknown,error).
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:- use_module(library(lists)).
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:- initialization(main).
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main :-
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unix( argv([H|_]) ), number_atom(N,H),
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f_permutations(N, MaxFlips),
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format('Pfannkuchen(~d) = ~d~n', [N, MaxFlips]),
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statistics,
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statistics_jit.
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% ------------------------------- %
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f_permutations(N, MaxFlips) :-
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numlist(1, N, L),
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f_permutations_(L, N, 0, 0, MaxFlips, 0, _).
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% ------------- %
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f_permutations_(L, N, I, MaxFlips0, MaxFlips, PermN0, PermN) :-
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(I < N ->
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(
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N =:= 1 ->
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!, processPerm(L, MaxFlips0, MaxFlips, PermN0, PermN)
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;
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N1 is N - 1,
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f_permutations_(L, N1, 0, MaxFlips0, MaxFlips1, PermN0, PermN1),
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split_list(L, N, Lt, Ld),
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rotateLeft(Lt, LtRL), append(LtRL, Ld, La), Ii is I + 1,
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!, f_permutations_(La, N, Ii, MaxFlips1, MaxFlips, PermN1, PermN)
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)
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;
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!, MaxFlips = MaxFlips0, PermN = PermN0
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).
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% ------------------------------- %
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flips(L, Flips) :- flips_(L, 0, Flips).
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flips_([1|_], Fla, Fla) :- !.
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flips_([N|T], Fla, Flips) :-
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take_drop([N|T], N, Lt, Ld), append(Lt, Ld, La),
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Fla1 is Fla + 1, !, flips_(La, Fla1, Flips).
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% ------------------------------- %
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rotateLeft([H|T], RL) :- append(T, [H], RL).
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rotateLeft([], []).
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% ------------------------------- %
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numlist(N, M, [N|Ls]) :- N < M, !, N1 is N + 1, numlist(N1, M, Ls).
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numlist(M, M, [M]).
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% ------------------------------- %
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printPerm([L|Ls]) :- write(L), printPerm(Ls).
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printPerm([]) :- nl.
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% ------------------------------- %
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processPerm(L, MaxFlips0, MaxFlips, PermN0, PermN) :-
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flips(L, Flips),
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(
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Flips > MaxFlips0 ->
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MaxFlips = Flips
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;
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MaxFlips = MaxFlips0
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),
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(
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PermN0 < 30 ->
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printPerm(L),
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PermN is PermN0 + 1
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;
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PermN = PermN0
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).
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% ------------------------------- %
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split_list([L|Ls], N, [L|Hs], Ts) :-
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N > 0, !, N1 is N - 1,
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split_list(Ls, N1, Hs, Ts).
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split_list(Ls, 0, [], Ls) :- !.
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% ------------------------------- %
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take_drop(L, N, Taken, Rest) :- take_drop_(L, N, 0, [], Taken, Rest).
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take_drop_(L, N, N, Ta, Ta, L) :- !.
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take_drop_([H|T], N, Nc, Ta, Taken, Rest) :-
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Nc1 is Nc + 1, !, take_drop_(T, N, Nc1, [H|Ta], Taken, Rest).
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% ------------------------------- %
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