为什么 SWI-Prolog 只给我第一个答案? [英] Why does SWI-Prolog only give me the first answer?

问题描述

我是 Prolog 的新手.我只是尝试简单的例子来学习.我有这个 .pl 文件，其中包含以下几行:

I'm new to Prolog. I'm just trying simple examples to learn. I have this .pl file with these lines:

parent(pam,bob).
parent(tom,bob).
parent(tom,lio).
parent(bob,ann).
parent(bob,pat).
parent(pat,jim).

经过咨询和测试，只显示第一个答案.例如:

After consulting and testing, it only shows the first answer. For example:

5 ?- parent(X,Y).
X = pam,
Y = bob .

不是应该给出满足关系parent的所有组合吗?

Isn't it supposed to give all the combinations that satisfy the relation parent?

有人知道问题出在哪里吗?

Do anyone have idea what the problem is?

推荐答案

在显示第一个结果后不要按 Enter，而是使用空格键

don't hit enter after your first results shows, use spacebar instead

• [Enter] 即使回溯尚未完成也停止执行
• [Spacebar] 或 [;] 继续从上一个结果回溯到下一个结果或 false 如果没有其他结果离开了.

• [Enter] stops execution even if the backtracking is not completed yet
• [Spacebar] or [;] continues with backtracking from your last result to the next result or false if there are no other results left.

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