Recursion 如何表达;“祖先”;递归地
我被这个递归卡住了,它不像我期望的那样工作 我的错在哪里Recursion 如何表达;“祖先”;递归地,recursion,prolog,transitive-closure,Recursion,Prolog,Transitive Closure,我被这个递归卡住了,它不像我期望的那样工作 我的错在哪里 #!/usr/bin/prolog % Facts mother( jeanne , michel ). % great-grandmother, grandfather mother( genevieve, aubin ). % grandmother, father mother( irene , alain ). % great-grandmother, grandfather mother( emilie
#!/usr/bin/prolog
% Facts
mother( jeanne , michel ). % great-grandmother, grandfather
mother( genevieve, aubin ). % grandmother, father
mother( irene , alain ). % great-grandmother, grandfather
mother( emilie , colette ). % great-grandmother, grandmother
mother( colette , muriel ). % grandmother, mother
mother( muriel , eve ). % mother, daughter
father( joseph , michel ). % great-grandfather, grandfather
father( michel , aubin ). % grandfather, father
father( xxx , alain ). % great-grandfather, grandfather
father( marcel , colette ). % great-grandfather, grandmother
father( alain , muriel ). % grandfather, mother
father( aubin , eve ). % father, daughter
% Rules
parent( Mother, Child ) :- mother( Mother, Child ).
parent( Father, Child ) :- father( Father, Child ).
ancestors( [Parent|Ancestors], Child ) :-
parent( Parent, Child ),
ancestors( Ancestors, Parent ).
% Queries
:-
ancestors( Ancestor, eve ),
format( 'Eve ancestors: ~w~n', Ancestor ).
% expected answer is [muriel, colette, alain, emilie, marcel, irene, xxx, aubin, michel, genevieve, joseph, jeanne]
编辑这是最终解决方案,谢谢大家
#!/usr/bin/prolog
/*##- Facts -##*/
mother( jeanne , michel ).
mother( genevieve, sylvie ).
mother( genevieve, brigitte ).
mother( genevieve, aubin ).
mother( irène , alain ).
mother( émilie , colette ).
mother( colette , muriel ).
mother( colette , olivier ).
mother( colette , audrey ).
mother( colette , stéphane ).
mother( muriel , eve ).
father( joseph , michel ).
father( michel , sylvie ).
father( michel , brigitte ).
father( michel , aubin ).
father( séraphin, alain ).
father( marcel , colette ).
father( alain , muriel ).
father( alain , olivier ).
father( yves , audrey ).
father( yves , stéphane ).
father( aubin , eve ).
/*##- Rules -##*/
parent( Mother, Child ) :- mother( Mother, Child ).
parent( Father, Child ) :- father( Father, Child ).
ancestor( Parent, Child ) :- parent( Parent, Child ).
ancestor( GrandParent, Child ) :-
parent( GrandParent, Parent ),
ancestor( Parent, Child ).
grandMothers( GrandMother, Child ) :-
mother( GrandMother, FatherOrMother ),
parent( FatherOrMother, Child ).
grandsFathers( GrandsFather, Child ) :-
father( GrandsFather, FatherOrMother ),
parent( FatherOrMother, Child ).
parents( Mother, Father, Child ) :-
father( Father, Child ),
mother( Mother, Child ).
strictSiblings( SisterOrBrother, Child ) :-
parents( Mother, Father, Child ),
parents( Mother, Father, SisterOrBrother ),
SisterOrBrother \= Child.
siblings( SisterOrBrother, Child ) :-
mother( Mother, Child ), mother( Mother, SisterOrBrother ), SisterOrBrother \= Child ;
father( Father, Child ), father( Father, SisterOrBrother ), SisterOrBrother \= Child .
/*##- Queries -##*/
theMother :-
mother( Mother, eve ),
format( 'Ève\'s mother: ~w~n', [Mother] ).
theFather :-
father( Father, eve ),
format( 'Ève\'s father: ~w~n', [Father] ).
theParents :-
setof( MotherOrFather, parent( MotherOrFather, eve ), MotherAndFather ),
format( 'Ève\'s parents: ~w~n', [MotherAndFather] ).
theGrandMothers :-
setof( GrandMother, grandMothers( GrandMother , eve ), GrandMothers ),
format( 'Ève\'s grand-mothers: ~w~n', [GrandMothers] ).
theGrandFathers :-
setof( GrandsFather, grandsFathers( GrandsFather , eve ), GrandsPères ),
format( 'Ève\'s grand-fathers: ~w~n', [GrandsPères] ).
lesEnfants :-
setof( Child, parents( genevieve, michel, Child ), Children ),
format( 'Geneviève and Michel children: ~w~n', [Children] ).
theTwoParents :-
parents( Mother, Father, eve ),
format( 'Ève\'s mother and father: ~w, ~w~n', [Mother, Father] ).
theStrictSiblings :-
setof( SisterOrBrother, strictSiblings( SisterOrBrother, muriel ), SistersAndBrothers ),
format( 'Muriel\'s strict siblings: ~w~n', [SistersAndBrothers] ).
theSiblings :-
setof( SisterOrBrother, siblings( SisterOrBrother, muriel ), SistersAndBrothers ),
format( 'Muriel\'s siblings: ~w~n', [SistersAndBrothers] ).
theAncestors :-
setof( Ancestor, ancestor( Ancestor, eve ), Ancestors ),
format( 'Ève\'s ancestors: ~w~n', [Ancestors] ).
:-
theMother,
theFather,
theParents,
theGrandMothers,
theGrandFathers,
lesEnfants,
theTwoParents,
theStrictSiblings,
theSiblings,
theAncestors,
halt( 0 ).
输出为:
Ève's mother: muriel
Ève's father: aubin
Ève's parents: [aubin,muriel]
Ève's grand-mothers: [colette,genevieve]
Ève's grand-fathers: [alain,michel]
Geneviève and Michel children: [aubin,brigitte,sylvie]
Ève's mother and father: muriel, aubin
Muriel's strict siblings: [olivier]
Muriel's siblings: [audrey,olivier,stéphane]
Ève's ancestors: [alain,aubin,colette,genevieve,irène,jeanne,joseph,marcel,michel,muriel,séraphin,émilie]
让我们以交互方式(在SWI Prolog中)执行此操作,而不是在脚本中使用
format/2
在最后打印答案
我们希望在列表中列出所有可能的eve
祖先
所以我们必须
祖先(A,eve)
bagof/3
、setof/3
或findall/3
中的一个来完成的,该谓词回溯目标答案,并将一个变量与一个包含所有答案的列表相统一(对于bagof/3
有重复答案,对于setof/3
没有重复答案,以及“无可能答案”)产生[]
而不是findall/3
的故障)
所以我们只需要确保找到祖先的目标是正确的
我们可以声明A
是C
的祖先,如果
是A
的父级;或C
是某些A
的父代,D
是D
C
A
成为C
的祖先……这是一个合理的“封闭世界假设”)
上面的公式非常适合Prolog的搜索策略,它试图首先解决正文中最左边的子目标:
ancestor(A,C) :- parent(A,C).
ancestor(A,C) :- parent(A,D),ancestor(D,C).
以“检查左边的祖先”的方式进行:
应该会产生相同的结果,但实际上不会:在最初给出正确答案后,Prolog处理器最终将进入一个无限循环,其中祖先(A,C)
调用祖先(A,D)
。(这将在更简单的“数据日志”语言中工作)
不管怎样,我们结束了吗
?- ancestor(X,eve).
X = muriel ;
X = aubin ;
X = jeanne ;
X = genevieve ;
X = irene ;
X = emilie ;
X = colette ;
X = joseph ;
X = michel ;
X = xxx ;
X = marcel ;
X = alain ;
false.
现在将所有内容收集到列表中:
(在SWI Prolog中,您必须说您希望打印长列表,而不是用省略号代替,所以):
然后:
?- bagof(X,ancestor(X,eve),Out).
Out = [muriel,aubin,jeanne,genevieve,irene,emilie,
colette,joseph,michel,xxx,marcel,alain].
在阅读本文之前,递归很容易,它可以帮助我们轻松找到解决方案。:)你刚刚忘记了递归的基本情况。我建议选择一个专门描述问题的标题。非常感谢,我已经将你的建议整合到我的样本(研究)中,并使用了很长的名称(我不喜欢a、C、D),并且对写祖先(祖父母、孩子)感到惊讶。我的错误就在这里。您的解决方案非常清晰。@Aubin近几个月来,我已从“长名称”切换到“短名称”,除非逻辑复杂且需要“就地文档”。之后更容易扫描源代码并找出变量。。。减少视觉噪音。由于变量总是子句局部的,所以在给定的上下文中没有那么多。(但我真的希望看到编辑器对变量着色的支持)。
?- set_prolog_flag(answer_write_options,[max_depth(0)]).
true.
?- bagof(X,ancestor(X,eve),Out).
Out = [muriel,aubin,jeanne,genevieve,irene,emilie,
colette,joseph,michel,xxx,marcel,alain].