4.2 逻辑范式——当算法失去了控制

/*快速排序法的Prolog实现 */
/* 定义划分法 */
partition(_,[],[],[]).                             /* 划分递归终点 */
partition(Pivot,[X|Rest],[X|Small],Big) :- 
X < Pivot, partition(Pivot,Rest,Small,Big).        /* 比基准小的归入Small */
partition(Pivot,[X|Rest],Small,[X|Big]) :- 
X >= Pivot, partition(Pivot,Rest,Small,Big).       /* 比基准大的归入Big */

/* 定义排序法 */
qsort([],[]).                                      /* 排序递归终点 */
qsort([Pivot|Rest],Sorted) :- 
partition(Pivot,Rest,Small,Big),                   /* 按基准划分子列 */
      qsort(Small,SortedSmall),                    /* 对前面的子列递归 */
      qsort(Big,SortedBig),                        /* 对后面的子列递归 */
      append(SortedSmall,[Pivot|SortedBig],Sorted)./* 子列合并 */ 

/* X is bachelor if X is unmarried and male*/
bachelor (X) :- unmarried(X) , male(X). 

class Person
{
    private Person parent;
    private boolean isMale;

    public Person(Person parent, boolean isMale)
    {
        this.isMale = isMale;
        this.parent = parent;
    }

    private boolean isSibling(Person other)
    {
        return parent == other.parent && parent != null && this != other;
    }

    public String getRelation(Person other)
    {
        if (other == null || this == other) return null;

        if (parent == other) return isMale ? "son" : "daughter";

        if (other.parent == this) return isMale ? "father" : "mother";

        if (parent == null) // this是老祖宗
        {
            if (other.parent == null) return null;

            if (other.parent.parent == this) return isMale ? "grandfather" : "grandmother";

            return null;
        }

        if (other.parent == null) // other是老祖宗
        {
            if (parent.parent == other) return isMale ? "grandson" : "granddaughter";

            return null;
        }

        // 非直系
        if (isSibling(other)) return isMale ? "brother" : "sister";

        if (parent.isSibling(other.parent)) return "cousin";

        if (parent.isSibling(other)) return isMale ? "nephew" : "niece";

        if (isSibling(other.parent)) return isMale ? "uncle" : "aunt";

        return null;
    }

    public static void main(String[] args)
    {
        Person a = new Person(null, true);
        Person b = new Person(a, true);
        Person c = new Person(a, true);
        Person d = new Person(a, false);
        Person e = new Person(b, false);
        Person f = new Person(b, true);
        Person g = new Person(c, false);
        Person h = new Person(d, true);
        Person i = new Person(d, false);
        Person j = new Person(d, true);
        // 以下省略。。。
     }
}

/* 规则 */
/* 上下两代直系关系 */
father(X,Y)        :- parent(X,Y), male(X).
mother(X,Y)        :- parent(X,Y), female(X).
child(X,Y)         :- parent(Y,X).
son(X,Y)           :- parent(Y,X), male(X).
daughter(X,Y)      :- parent(Y,X), female(X).

/* 祖孙关系 */
grandparent(X,Y)   :- parent(X,Z), parent(Z,Y).
grandfather(X,Y)   :- grandparent(X,Y), male(X).
grandmother(X,Y)   :- grandparent(X,Y), female(X).
grandchild(X,Y)    :- grandparent(Y,X).
grandson(X,Y)      :- grandparent(Y,X), male(X).
granddaughter(X,Y) :- grandparent(Y,X), female(X).

/* 平辈关系 */
/* 若X与Y有相同的父辈Z，且X不是Y，则X与Y是同胞*/
sibling(X,Y)       :- parent(Z,X), parent(Z,Y), X\==Y. 
brother(X,Y)       :- sibling(X,Y), male(X).
sister(X,Y)        :- sibling(X,Y), female(X).
cousin(X,Y)        :- parent(Z,X), parent(W,Y), sibling(Z,W).

/* 上下两代旁系关系 */
uncle(X,Y)         :- parent(Z,Y), brother(X,Z).
aunt(X,Y)          :- parent(Z,Y), sister(X,Z).
nephew(X,Y)        :- parent(Z,X), sibling(Z,Y), male(X).
niece(X,Y)         :- parent(Z,X), sibling(Z,Y), female(X).

/* 定义一个普适关系relation，方便查询 */
relation(R, X, Y)       :-  relations(Rs), member(R,Rs), Q =..[R,X,Y], call(Q).

/* 事实 */
/* 关系列表 */
relations([parent,father,mother,son,daughter,grandparent,grandfather,
grandmother,grandchild,grandson,granddaughter,
                sibling,brother,sister,cousin,uncle,aunt,nephew,niece]).

parent(a,b). parent(a,c). parent(a,d).
parent(b,e). parent(b,f).
parent(c,g).
parent(d,h). parent(d,i). parent(d,j).

male(a).
male(b).
male(c).
female (d).
female (e).
male(f).
female (g).
male(h).
female (i).
male(j). 

/* 规则 */
/* 配偶原则 */
father(X,Y)          :- spouse(Z,X), mother(Z,Y).
mother(X,Y)        :- spouse(Z,X), father(Z,Y).
husband(X,Y)      :- spouse(X,Y), male(X).
wife(X,Y)            :- spouse(X,Y), female(X).

/* 父系的堂、姑兄弟姐妹 */
paternal_cousin(X,Y) :- father(Z,X), father(W,Y), sibling(Z,W).
/* 母系的舅、姨兄弟姐妹 */
maternal_cousin(X,Y) :- mother(Z,X), mother(W,Y), sibling(Z,W).

/* 姻亲关系 */
father_in_law(X,Y) :- spouse(Y,Z), father(X,Z).
mother_in_law(X,Y) :- spouse(Y,Z), mother(X,Z).
son_in_law(X,Y)    :- spouse(X,Z), daughter(Z,Y).
daughter_in_law(X,Y) :- spouse(X,Z), son(Z,Y).

/* 曾祖孙关系 */
great_grandparent(X,Y) :- grandparent(Z,Y), parent(X,Z).
great_grandchild(X,Y)  :- grandchild(Z,Y), child(X,Z).

/* 事实 */
/* 新引入的关系 */
relations([husband,wife, paternal_cousin,maternal_cousin,
father_in_law,mother_in_law,son_in_law,daughter_in_law,
great_grandparent,great_grandchild]).

parent(pa,a).
spouse(a,as).
spouse(ds,d).
spouse(cs,c). 

输入查询：relation(R,a,ds) /* a与ds的关系是什么？ */

输出结果：R=father_in_law

输入查询：great_grandparent (pa,X) /* pa是谁的曾祖？*/

输出结果：X=e;X=f;X=g; X=h; X=i; X=j;