Prolog 查询返回 H128 [英] Prolog Query returning H128

问题描述

在下面的查询中，首先我得到 X = H128，它来自哪里?另外为什么它返回是?是不是因为变量 X 实际上没有定义而我们正在测试该条件?

In the query below, firstly I'm getting X = H128, where does that come from? Also why is it returning yes? Is it because the variable X is actually not defined and we are testing for that condition?

?- not(X==3).
X = H128 
yes

推荐答案

您的查询正在使用未实例化的变量 (X).当检查 X 是否用术语 3 it (X==3) 实例化时，它失败，因为 X 未实例化.

Your query is using an uninstantiated variable (X). When checking whether X is instantiated with the term 3 it (X==3) it fails because X is uninstantiated.

因此，not(X==3) 会成功，因为 prolog 引擎无法证明 X==3.因此，您的序言解释器返回是"(由于解释器的失败方法否定)，并且 X 保持未实例化.

Therefore, not(X==3) will succeed as the prolog engine cannot prove X==3. Your prolog interpreter is thus returning 'yes' (due to the negation as failure approach of the interpreter), and X remains uninstantiated.

这就是解释器显示 X = H128 的原因，其中 H128 是一个虚拟的未实例化变量.

That is why the interpreter shows X = H128, where H128 is a dummy uninstantiated variable.

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