Data commit

Task/Best-shuffle/Prolog/best-shuffle-1.pro

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+:- dynamic score/2.
+
+best_shuffle :-
+	maplist(best_shuffle, ["abracadabra", "eesaw", "elk", "grrrrrr",
+			       	"up", "a"]).
+
+best_shuffle(Str) :-
+	retractall(score(_,_)),
+	length(Str, Len),
+	assert(score(Str, Len)),
+	calcule_min(Str, Len, Min),
+	repeat,
+	   shuffle(Str, Shuffled),
+	   maplist(comp, Str, Shuffled, Result),
+	   sumlist(Result, V),
+	   retract(score(Cur, VCur)),
+	   (  V < VCur -> assert(score(Shuffled, V)); assert(score(Cur, VCur))),
+	   V = Min,
+	retract(score(Cur, VCur)),
+	writef('%s : %s (%d)\n', [Str, Cur, VCur]).
+
+comp(C, C1, S):-
+	(   C = C1 -> S = 1; S = 0).
+
+% this code was written by P.Caboche and can be found here :
+% http://pcaboche.developpez.com/article/prolog/listes/?page=page_3#Lshuffle
+shuffle(List, Shuffled) :-
+  length(List, Len),
+  shuffle(Len, List, Shuffled).
+
+shuffle(0, [], []) :- !.
+
+shuffle(Len, List, [Elem|Tail]) :-
+  RandInd is random(Len),
+  nth0(RandInd, List, Elem),
+  select(Elem, List, Rest),
+  NewLen is Len - 1,
+  shuffle(NewLen, Rest, Tail).
+
+
+% letters are sorted out then packed
+% If a letter is more numerous than the rest
+% the min is the difference between the quantity of this letter and
+% the sum of the quantity of the other letters
+calcule_min(Str, Len, Min) :-
+	msort(Str, SS),
+	packList(SS, Lst),
+	sort(Lst, Lst1),
+	last(Lst1, [N, _]),
+	(   N * 2 > Len -> Min is 2 * N - Len; Min = 0).
+
+
+
+% almost the same code as in "run_length" page
+packList([],[]).
+
+packList([X],[[1,X]]) :- !.
+
+
+packList([X|Rest],[XRun|Packed]):-
+    run(X,Rest, XRun,RRest),
+    packList(RRest,Packed).
+
+
+run(Var,[],[1,Var],[]).
+
+run(Var,[Var|LRest],[N1, Var],RRest):-
+    run(Var,LRest,[N, Var],RRest),
+    N > 0,
+    N1 is N + 1.
+
+
+run(Var,[Other|RRest], [1,Var],[Other|RRest]):-
+     dif(Var,Other).

Task/Best-shuffle/Prolog/best-shuffle-2.pro

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+:- system:set_prolog_flag(double_quotes,codes) .
+
+play(STRINGs)
+:-
+shuffle(STRINGs,SHUFFLEDs) ,
+score(STRINGs,SHUFFLEDs,SCORE) ,
+system:format('~s , ~s , (~10r)~n',[STRINGs,SHUFFLEDs,SCORE])
+.
+
+test
+:-
+play("abracadabra") ,
+play("seesaw") ,
+play("elk") ,
+play("grrrrrr") ,
+play("up") ,
+play("a")
+.
+
+%! shuffle(Xs0,Ys) .
+%
+% The list `Ys` is an random permutation of the list `Xs0` .
+% No assumption is made about the nature of each item in the list .
+%
+% The default seed for randomness provided by the system is truly random .
+% Set the seed explicitly with `system:set_random(seed(SEED))` .
+
+:- op(1,'xfy','shuffle_') .
+
+shuffle(Xs0,Ys)
+:-
+(assign_randomness) shuffle_ (Xs0,Ys0) ,
+(sort) shuffle_ (Ys0,Ys1) ,
+(remove_randomness) shuffle_ (Ys1,Ys)
+.
+
+/*
+1. assign an random number to each of the items in the list .
+2. sort the list of items according to the random number assigned to each item .
+3. remove the random number from each of the items in the list .
+*/
+
+(assign_randomness) shuffle_ ([],[]) :- ! .
+
+(assign_randomness) shuffle_ ([X0|Xs0],[sortable(R,X0)|Rs])
+:-
+system:random(R) ,
+(assign_randomness) shuffle_ (Xs0,Rs)
+.
+
+(sort) shuffle_ (Rs0,Ss)
+:-
+prolog:sort(Rs0,Ss)
+.
+
+(remove_randomness) shuffle_ ([],[]) :- ! .
+
+(remove_randomness) shuffle_ ([sortable(_R0,X0)|Ss0],[X0|Xs])
+:-
+(remove_randomness) shuffle_ (Ss0,Xs)
+.
+
+
+%! score(Xs0,Ys0,SCORE) .
+%
+% `SCORE` is the count of positions in Ys0 that
+% have the identical content as
+% the content in the same position in Xs0 .
+
+score([],[],0) :- ! .
+
+score([X0|Xs0],[Y0|Ys0],SCORE)
+:-
+X0 = Y0 ,
+! ,
+score(Xs0,Ys0,SCORE0) ,
+SCORE is SCORE0 + 1
+.
+
+score([_|Xs0],[_|Ys0],SCORE)
+:-
+! ,
+score(Xs0,Ys0,SCORE)
+.