强制Prolog选择变量的唯一值 [英] Force Prolog to choose unique values of variables
问题描述
好吧,我是Prolog的新手,请原谅,如果这很琐碎,但是我似乎找不到合适的优雅答案.我正在尝试在 learnprolognow.org ,练习2.4(填字游戏).
OK I am new to Prolog, so excuse me if this is something trivial, but I can't seem to find a proper elegant answer to this. I am trying to work out the exercise here on learnprolognow.org, exercise 2.4 (the crossword).
该练习提供了以下事实:
The exercise provides these facts:
word(astante, a,s,t,a,n,t,e).
word(astoria, a,s,t,o,r,i,a).
word(baratto, b,a,r,a,t,t,o).
word(cobalto, c,o,b,a,l,t,o).
word(pistola, p,i,s,t,o,l,a).
word(statale, s,t,a,t,a,l,e).
我想出的解决每个单词的填字游戏位置的方法是:
And the solution I came up with to solve the crossword placement of each word is this:
crossword(V1, V2, V3, H1, H2, H3) :-
word(V1, V1a, V1bH1b, V1c, V1dH2b, V1e, V1fH3b, V1g),
word(V2, V2a, V2bH1d, V2c, V2dH2d, V2e, V2fH3d, V2g),
word(V3, V3a, V3bH1f, V3c, V3dH2f, V3e, V3fH3f, V3g),
word(H1, H1a, V1bH1b, H1c, V2bH1d, H1e, V3bH1f, H1g),
word(H2, H2a, V1dH2b, H2c, V2dH2d, H2e, V3dH2f, H2g),
word(H3, H3a, V1fH3b, H3c, V2fH3d, H3e, V3fH3f, H3g).
V1a
至V1g
等是每个单词的字符,而V1bH1b
至V3fH3f
是填字游戏中单词之间的共同字符.
With V1a
to V1g
etc. being the characters of each word, and the V1bH1b
to V3fH3f
being the characters in common between words in the crossword.
该解决方案似乎可行,但是结果产生了重复的值,第一个结果是:
The solution seems to work, however the result is producing duplicate values, with the first result being:
?- crossword(V1, V2, V3, H1, H2, H3).
V1 = astante,
V2 = baratto,
V3 = statale,
H1 = astante,
H2 = baratto,
H3 = statale .
如何强制Prolog具有V1 \= V2 \= V3 \= H1 \= H2 \= H3
?
如果我一个接一个地做它们,我将需要120个排列,所以必须有一种更快的方法,这是初学者的练习,所以我一定会缺少一些东西.
How can I force Prolog to have V1 \= V2 \= V3 \= H1 \= H2 \= H3
?
If I do them individually one by one I will need 120 permutations, so there must be a quicker way, and this is a beginners exercise so I must be missing something.
我发现了这相似的问题,但提供的答案似乎太复杂了,我希望有一种更简单的方法.我在Ubuntu上使用swi-prolog,以防万一.
I found this similar question, but the answers provided seem so complicated, I hope there is a simpler way. I am using swi-prolog on Ubuntu, just in case it matters.
谢谢.
推荐答案
使用alldif/1
定义如下:
alldif([]).
alldif([E|Es]) :-
maplist(dif(E), Es),
alldif(Es).
甚至可以用于最一般的查询:
Which can be used even for the most general query:
?- alldif(Es).
Es = [] ;
Es = [_G1924] ;
Es = [_G2061, _G2064],
dif(_G2061, _G2064) ;
Es = [_G2163, _G2166, _G2169],
dif(_G2163, _G2169),
dif(_G2163, _G2166),
dif(_G2166, _G2169) ;
Es = [_G2309, _G2312, _G2315, _G2318],
dif(_G2309, _G2318),
dif(_G2309, _G2315),
dif(_G2309, _G2312),
dif(_G2315, _G2318),
dif(_G2312, _G2315),
dif(_G2312, _G2318) ...
目标maplist(dif(E),Es)
的含义可以通过查看答案得到最好的理解:
The meaning of the goal maplist(dif(E),Es)
is best understood by looking at the answers:
?- maplist(dif(E),Es).
Es = [] ;
Es = [_G1987],
dif(E, _G1987) ;
Es = [_G2040, _G2043],
dif(E, _G2043),
dif(E, _G2040) ;
Es = [_G2093, _G2096, _G2099],
dif(E, _G2099),
dif(E, _G2096),
dif(E, _G2093) ;
Es = [_G2146, _G2149, _G2152, _G2155],
dif(E, _G2155),
dif(E, _G2152),
dif(E, _G2149),
dif(E, _G2146) ...
也就是说,Es
是与E
不同的所有元素的列表.目标 maplist(dif(E),[ A,B,C])将第一个元素(在本例中为dif(E)
)与列表中的每个元素组合在一起.因此dif(E,A), dif(E,B), dif(E,C)
.
That is, Es
is a list of elements that are all different to E
. The goal maplist(dif(E),[A,B,C]) combines the first element (in this case dif(E)
) with each element of the list. Thus dif(E,A), dif(E,B), dif(E,C)
.
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