44 lines
993 B
Prolog
44 lines
993 B
Prolog
look_and_say(L) :-
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maplist(write, L), nl,
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encode(L, L1),
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look_and_say(L1).
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% This code is almost identical to the code of "run-length-encoding"
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encode(In, Out) :-
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packList(In, R1),
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append(R1,Out).
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% use of library clpfd allows packList(?In, ?Out) to works
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% in both ways In --> Out and In <-- Out.
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:- use_module(library(clpfd)).
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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%
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% ?- packList([a,a,a,b,c,c,c,d,d,e], L).
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% L = [[3,a],[1,b],[3,c],[2,d],[1,e]] .
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% ?- packList(R, [[3,a],[1,b],[3,c],[2,d],[1,e]]).
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% R = [a,a,a,b,c,c,c,d,d,e] .
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%
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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packList([],[]).
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packList([X],[[1,X]]) :- !.
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packList([X|Rest],[XRun|Packed]):-
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run(X,Rest, XRun,RRest),
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packList(RRest,Packed).
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run(Var,[],[1,Var],[]).
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run(Var,[Var|LRest],[N1, Var],RRest):-
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N #> 0,
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N1 #= N + 1,
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run(Var,LRest,[N, Var],RRest).
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run(Var,[Other|RRest], [1,Var],[Other|RRest]):-
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dif(Var,Other).
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