用软件构造的思想解决猴子摘香蕉问题

  • 背景简介/问题描述

一个房间里,天花板上挂有一串香蕉,有一只猴子可在房间里任意活动(到处走动,推移箱子,攀登箱子等)。设房间里还有一只可被猴子移动的箱子,且猴子登上箱子时才能摘到香蕉,问猴子在某一状态下(设猴子位置为A,香蕉位置在B,箱子位置为C),如何行动可摘取到香蕉

  • 算法介绍

2.1 猴子摘香蕉问题PEAS

性能

环境

执行器

感知器

猴子站在箱子上

香蕉

Move

Site

猴子摘到香蕉

箱子

Climb

Hold

位置

Push

On

Grasp

Hang

Jump

2.2定义谓词

Site(x,w):物体x的位置是w

Hold(z):z手中拿着香蕉

On(z):z站在了箱子上

Hang(y,w):y悬挂在位置w

2.3定义变元定义域:

x∈{猴子,箱子}

y∈{香蕉}

z∈{猴子}

w∈{a,b,c}

2.4定义操作:

Move(u,v):猴子从u走到v

Climb():猴子爬上了箱子

Push(u,v):猴子推着箱子从u走到v

Grasp():猴子拿到了香蕉

Jump():猴子从箱子上跳下来

2.5定义初始状态与目标状态

S0=Site(Monkey,a)

^Hang(Banana,b)

^Site(Box,c)

^¬On(Monkey)

^¬Holds(Monkey)

Sg=Site(Monkey,b)

^¬Hang(Banana,b)

^Site(Box,b)

^¬On(Monkey)

^Holds(Monkey)

2.6各操作条件与动作

Move(u,v)

条件:¬On(Monkey),Site(Monkey,u)

动作:删除表:Site(Monkey,u) 添加表Site(Monkey,v)

Push(v,u)

条件:¬On(Monkey),Site(Monkey,v),Site(Box,v)

动作:删除表:Site(Monkey,v);Site(Box,v)

添加表:Site(Monkey,w);Site(Box,w)

Climb()

条件:¬On(Monkey),Site(Monkey,v),Site(Box,v)

动作:删除表:¬On(Monkey)

   添加表:On(Monkey)

Grasp()

条件:On(Monkey),Site(Box,b),Hang(Banana,b)

动作:删除表: ¬Holds(Monkey),Hang(Banana,b)

   添加表:Holds(Monkey),¬Hang(Banana,b)

Jump()

条件:Hold(Monkey),On(Monkey)

动作:删除表:On(monkey)

添加表:¬On(monkey)

2.7求解过程

S0=Site(Monkey,a)

^Hang(Banana,b)

^Site(Box,c)

^¬On(Monkey)

^¬Holds(Monkey)

——执行Move(u,v)

S1=Site(Monkey,c)

^Hang(Banana,b)

^Site(Box,c)

^¬On(Monkey)

^¬Holds(Monkey)

——执行Push(v,w)

S2=Site(Monkey,b)

^Hang(Banana,b)

^Site(Box,b)

^¬On(Monkey)

^¬Holds(Monkey)

——执行Climb()

S3=Site(Monkey,b)

^Hang(Banana,b)

^Site(Box,b)

^On(Monkey)

^¬Holds(Monkey)

——执行Grasp()

S4=Site(Monkey,b)

^¬Hang(Banana,b)

^Site(Box,b)

^On(Monkey)

^Holds(Monkey)

——执行Jump()

Sg=Site(Monkey,b)

^¬Hang(Banana,b)

^Site(Box,b)

^¬On(Monkey)

^Holds(Monkey)

  • 算法实现

3.1 实验代码

Banana类

package monkey;

public class Banana {

    private final Position banana_position=new Position();

    private boolean Hang=true;

    public Position getBanana_position() {

        return banana_position;

    }

    public void setBanana_position(int x,int y){

        banana_position.setPosition(x,y);

    }

    public boolean isHang() {

        return Hang;

    }

    public void Grasp(){

        Hang=false;

    }

}

Box类

package monkey;

public class Box {

    private final Position box_position=new Position();

    private boolean OnBox=false;

    public void setBox_position(int x,int y){

        box_position.setPosition(x,y);

    }

    public void Push(Monkey monkey,int x,int y){

        monkey.Move(x,y);

        System.out.println("the box is being pushed from("+box_position.getX()+','

                +box_position.getY()+")to("+x+','+y+")");

        box_position.setPosition(x,y);

    }

    public void Jump(){

        if(OnBox){

            OnBox=false;

            System.out.println("the monkey has jumped off the box");

        }

        else{

            System.out.println("the monkey is standing under the box");

        }

    }

    public void Climb(){

        if(!OnBox){

            OnBox=true;

            System.out.println("the monkey has climbed on the box");

        }

        else{

            System.out.println("the monkey is standing on the box");

        }

    }

    public Position getBox_position() {

        return box_position;

    }

    public boolean isOnBox() {

        return OnBox;

    }

}

Monkey类

package monkey;

public class Monkey {

    private final Position monkey_position=new Position();

    public void setMonkey_position(int x,int y) {

        monkey_position.setPosition(x,y);

    }

    public void Move (int x,int y){

        System.out.println("the monkey is going from("+monkey_position.getX()+','

                +monkey_position.getY()+")to("+x+','+y+")");

        monkey_position.setPosition(x,y);

    }

    public Position getMonkey_position(){

        return monkey_position;

    }

}

Position类

package monkey;

import java.util.Objects;

public class Position {

    private int x;

    private int y;

    public int getX() {

        return x;

    }

    public int getY() {

        return y;

    }

    public void setPosition(int x,int y){

        this.x=x;

        this.y=y;

    }

    @Override

    public boolean equals(Object o) {

        if (this == o) return true;

        if (o == null || getClass() != o.getClass()) return false;

        Position position = (Position) o;

        return x == position.x && y == position.y;

    }

    @Override

    public int hashCode() {

        return Objects.hash(x, y);

    }

}

Main类

package monkey;

import java.util.Scanner;

import static java.lang.System.exit;

public class main {

    public static void main(String[] args) {

        int x,y;

        Monkey monkey = new Monkey();

        Banana banana = new Banana();

        Box box = new Box();

        Scanner sc =new Scanner(System.in);

        System.out.println("Please Enter the position of the banana(x,y):");

        x=sc.nextInt();

        y=sc.nextInt();

        banana.setBanana_position(x,y);

        System.out.println("the banana is hanging at ("+banana.getBanana_position().getX()+','

                +banana.getBanana_position().getY()+')');

        System.out.println("Please Enter the position of the box(x,y):");

        x=sc.nextInt();

        y=sc.nextInt();

        box.setBox_position(x,y);

        System.out.println("the box is at ("+box.getBox_position().getX()+','

                +box.getBox_position().getY()+')');

        System.out.println("Please Enter the position of the monkey(x,y):");

        x=sc.nextInt();

        y=sc.nextInt();

        monkey.setMonkey_position(x,y);

        System.out.println("the monkey is at ("+monkey.getMonkey_position().getX()+','

                +monkey.getMonkey_position().getY()+')');

        if(!monkey.getMonkey_position().equals(box.getBox_position())){

            monkey.Move(box.getBox_position().getX(),box.getBox_position().getY());

        }

        if(!monkey.getMonkey_position().equals(banana.getBanana_position())){

            box.Push(monkey,banana.getBanana_position().getX(),banana.getBanana_position().getY());

        }

        box.Climb();

        banana.Grasp();

        if(!banana.isHang())

            System.out.println("the monkey has grasped the banana.");

        exit(0);

    }

}

  • 讨论及结论

 环境可理解为java的对象类,动作器可理解为方法,感受器可理解为参数,我们要尽可能防止表示泄露,因此设置参数用private、setter、getter的组合来传递以及更改参数,而且要时刻记得checkRep,此外猴子摘香蕉问题,猴子会主动搬箱子,抓取香蕉,以及爬上或跳下箱子。那我们在构造方法时应该在哪一个类中构建呢?我们主观印象会觉得猴子是主语,他做出了这些动作,应该将方法都添加到猴子类中,但事实上,我们会发现将方法添加到宾语,也就是箱子、香蕉这些类会更加方便,这是因为虽然猴子爬上或搬箱子,别的动物甚至某种类也可以完成这些动作,可以被搬,可以被攀爬或跳下是箱子的属性,因此我们在构造方法时要先判断好对谁创建一个方法,入参、返回值,规约,检查入口。这些对编写java程序至关重要。

参考文献

注:报告中图的下方要有图题(如图1. XXXX),表格需要用三线表,表头需列在表的上方(如表1. XXXX)。图表居中排列。

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