Question

% comment the next two lines out when testing - put back in to submit
:- initialization(q1).
:- initialization(q2).
:- initialization(q3).
:- initialization(end). 
% FACTS. 
mammal(kitty).
mammal(ratatat).
mammal(fido).
claws(kitty).
tail(ratatat).
bestfriend(fido).
feathers(tweety). 
% 9 RULES. 
% If X is a mammal then X has fur. 
fur(X) :- mammal(X).
% If X has fur and X has a tail then X is a rat. 
rat(X) :- fur(X),tail(X).
% If X has claws and X has fur then X is a cat.
cat(X) :- claws(X),fur(X).
% If X is a cat then X meows.
meows(X) :- cat(X).
% If X has feathers then X is a bird.
bird(X) :- feathers(X).
% If X is a bestfriend and X has fur then X is a dog.
dog(X) :- bestfriend(X),fur(X).
% If X is a dog and Y meows then X likes Y.
likes(X,Y) :- dog(X),meows(Y).
% If X is a cat and Y is a bird then X likes Y.
likes(X,Y) :- cat(X),bird(Y).
% If X is a cat and Y is a rat then X likes Y.
likes(X,Y) :- cat(X),rat(Y). 
writeln(T) :- write(T), nl. 
max(X,Y,Z) :-
  X > Y,
  X > Z,
  write(X).
max(X,Y,Z) :-
  X > Y,
  write(Z).
max(_,Y,Z) :-
  Y > Z,
  write(Y).
max(_,_,Z) :-
  write(Z).
moves(N,R) :-
N = 0, R is 0.
moves(N,R) :-
N = 1, R is 1.
moves(N,R) :-
N > 1, T1 is N - 1, T2 is N-1, moves(T1,R1), moves(T2,R2), R is R1 + R2 + 1. 
% QUERY. Uncomment after you have written all predicates.
q1 :- writeln('Who likes whom?'), 
      findall(X, (likes(X,Y), format('~w ~w~n',[X,Y])),_).
q2 :- write('Move cnt for 5: '),
      findall(X, (moves(5,X), format('~w' ,[X])),_).
q3 :-nl, write( 'Max(7,3,9)? '),
      findall(X, (max(7,3,9), format('~w ~n' ,[X])),_).
end :- writeln('done.'), halt.

输出：
谁喜欢谁？
fido kitty
kitty tweety
kitty ratatat
移动cnt为5：31
马克斯（7,3,9）？ 9_13＆lt; ----为什么打印和下划线13？
9_13＆lt; ---也为什么再次打印这一行？
完成。

不确定为什么它的打印方式是任何信息将不胜感激！我认为它与我的q3查询有关，但我一直在搞乱它并且无法弄明白，谢谢你们！

Answer 1

q3与q1，q2的共同点是findall / 3的一个不寻常的用法（我认为你应该使用forall / 2，真的）。与其他2个查询不同，q3输出无界变量（X不会出现在findall 目标中），并且它会执行2次，因为max / 3会成功2次。这是q3相关的跟踪，获得（在swipl中）添加指令:- initialization((leash(-all),trace)).。在gprolog中，它是:- initialization((leash(none),trace)).

   Call: (20) q3
   Call: (21) nl

   Exit: (21) nl
   Call: (21) write('Max(7,3,9)? ')
Max(7,3,9)? 
   Exit: (21) write('Max(7,3,9)? ')
^  Call: (21) findall(_G1900,  (max(7, 3, 9), format('~w ~n', [_G1900])), _G1912)
   Call: (27) max(7, 3, 9)
   Call: (28) 7>3
   Exit: (28) 7>3
   Call: (28) 7>9
   Fail: (28) 7>9
   Redo: (27) max(7, 3, 9)
   Call: (28) 7>3
   Exit: (28) 7>3
   Call: (28) write(9)
9
   Exit: (28) write(9)
   Exit: (27) max(7, 3, 9)
^  Call: (27) format('~w ~n', [_G1900])
_G1900 
^  Exit: (27) format('~w ~n', [_G1900])
   Redo: (27) max(7, 3, 9)
   Call: (28) 3>9
   Fail: (28) 3>9
   Redo: (27) max(7, 3, 9)
   Call: (28) write(9)
9
   Exit: (28) write(9)
   Exit: (27) max(7, 3, 9)
^  Call: (27) format('~w ~n', [_G1900])
_G1900 
^  Exit: (27) format('~w ~n', [_G1900])
^  Exit: (21) findall(_G1900, user: (max(7, 3, 9), format('~w ~n', [_G1900])), [_G1923, _G1920])
   Exit: (20) q3

任何人都可以解释为什么即时通讯我的prolog查询

1 个答案: