检查一个数是否为质数的 Prolog 程序 [英] Prolog Program To Check If A Number Is Prime

问题描述

我根据质数只能被1和它本身整除的逻辑编写了以下程序.所以我只是经历了将它除以所有大于一且小于自身的数字的过程，但我似乎遇到了问题，因为我将所有输入的数字都设为真.这是我的代码...

I wrote the following program based on the logic that a prime number is only divisible by 1 and itself. So I just go through the process of dividing it to all numbers that are greater than one and less than itself, but I seem to have a problem since I get all entered numbers as true. Here's my code...

divisible(X,Y) :-
    Y < X,
    X mod Y is 0,
    Y1 is Y+1,
    divisible(X,Y1).

isprime(X) :-
    integer(X),
    X > 1,
    \+ divisible(X,2).

提前致谢:)

推荐答案

我是 Prolog 的初学者，但设法解决了您的问题.

I'm a beginner in Prolog but managed to fix your problem.

divisible(X,Y) :- 0 is X mod Y, !.

divisible(X,Y) :- X > Y+1, divisible(X, Y+1).

isPrime(2) :- true,!.
isPrime(X) :- X < 2,!,false.
isPrime(X) :- not(divisible(X, 2)).

主要问题是声明X mod Y is 0.谓词is有两个(左右)参数，但左边的参数必须是一个常量或一个在谓词执行时已经统一的变量.我只是交换了这些值.其余代码用于检查数字 2(质数)和小于 2 的数字(非质数)

The main issue was the statement X mod Y is 0. Predicate is has two (left and right) arguments, but the left argument has to be a constant or a variable that is already unified at the moment that the predicate is executing. I just swapped these values. The rest of the code is for checking number 2 (which is prime) and number less than 2 (that are not primes)

我忘了提到比较 Y <X 有问题，因为您想测试 2 和 X-1 之间的所有数字，该比较包括 X.

I forgot to mention that the comparison Y < X is buggy, because you want to test for all numbers between 2 and X-1, that comparison includes X.

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