lists.pl

ｐｒｏｌｏｇ样例

/*****************************************************/
/* Prolog List Processing Examples                   */
/*****************************************************/

my_member(X,[X|_]).
my_member(X,[_|Y]) :- my_member(X,Y).

% my_length([],0).
% my_length([_|T],N) :- my_length(T,M), N is M + 1.

my_length(List,Length) :- 
   my_length(List,0,Length).

my_length([],Length,Length).
my_length([_|T],Acc,Length) :- 
   NewAcc is Acc + 1,
   my_length(T,NewAcc,Length).

smallest([H|T],S) :- smallest(T,H,S), !.

smallest([],S,S).
smallest([H|T],Acc,S) :- H < Acc, smallest(T,H,S).
smallest([H|T],Acc,S) :- smallest(T,Acc,S).

isort(L,S) :- isort(L,[],S), !.

isort([],S,S).
isort([H|T],Acc,S) :- insert(H,Acc,NewAcc),
                      isort(T,NewAcc,S).

insert(E,[],[E]).
insert(E,[H|T],[E|[H|T]]) :- E =< H.
insert(E,[H|T],[H|L]) :- insert(E,T,L).

% digits(+IntExpr,-List) and digits(-Int,+ListOfInt)

digits(N,D) :- integer(N), digits(N,[],D).
digits(N,D) :- var(N), value(D,0,N).

digits(N,Acc,[N|Acc]) :- N < 10, !.
digits(N,Acc,D)       :- H is N mod 10,
                         NewN is N // 10,
                         digits(NewN,[H|Acc],D).

value([],N,N).
value([H|T],Acc,N) :- integer(H),
                      H < 10,
                      AccNew is H + 10 * Acc,
                      value(T,AccNew,N).