我在下面的Prolog代码中做错了什么

时间:2017-06-03 17:00:09

标签: recursion prolog

该计划旨在检查学生是否已取得指定的课程清单。但即使学生已经取得课程列表,它也显示为假。我做错了什么?

代码:

 %Structure  Of facts

 %student(ID,FirstName,LastName,Advisor,CreditsPassed,GPA,CourseTakenList).
 %courses_taken(CourseId,CourseTitle, Credit,Grade, NoOfTimesRepeated).

   %Fact
   student(20135639,'Sara','Haider','Mr. Hussain Al-Arrayed',98,3.95,
   [courses_taken('ITCE418', 'PRODUCTIVITY WITH IS TECHNOLOGY',3,'A', 0),
    courses_taken('MATHS101', 'CALCULUS I', 3,'A', 0),
    courses_taken('ACC112', 'FINANCIAL ACCOUNTING I', 3, 'A', 0),
    courses_taken('ECON140', 'MICROECONOMICS', 3,'A', 0),
    courses_taken('ENGL219', 'TECHNICAL REPORT WRITING', 3,'A', 0)  ]  ).

 check_prereq([],Id):- !.
 check_prereq([course(P)]|T,Id):-
     student(Id,_,_,_,_,_, CoursesTakenList),
     member( courses_taken(P,_,_,_,_), CoursesTakenList),
     check_prereq(T,Id).

以下查询应返回true,因为学生已参加这些课程

 ?- check_prereq([course('ITCE418'), course('ACC112')],20135639).
 false.

我做错了吗?

1 个答案:

答案 0 :(得分:0)

您需要替换:import React from 'react' import ReactStreetview from 'react-streetview' import { streetViewPanoramaOptions } from './constants.js' const About = () => { const googleMapsApiKey = 'myAPIkey' return ( <div> <div style={{ .... }} > <ReactStreetview apiKey={googleMapsApiKey} streetViewPanoramaOptions={streetViewPanoramaOptions.hall} /> </div> <div style={{ .... }} > <ReactStreetview apiKey={googleMapsApiKey} streetViewPanoramaOptions={streetViewPanoramaOptions.firstRoom} /> </div> <div style={{ .... }} > <ReactStreetview apiKey={googleMapsApiKey} streetViewPanoramaOptions={streetViewPanoramaOptions.secondRoom} /> </div> </div> ) } export default About

[course(P)]|T with [course(P)|T]

同样在第一行用 check_prereq([],_):- !. check_prereq([course(P)|T],Id):- student(Id,_,_,_,_,_, CoursesTakenList), member( courses_taken(P,_,_,_,_), CoursesTakenList), check_prereq(T,Id). 替换Id(匿名变量)以消除警告(Singleton变量)。现在工作正常:

_

请注意,它返回true并要求更多解决方案返回false,但它会像我们预期的那样成功。

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