如何在Prolog中将元素添加到列表中? [英] How do you append an element to a list in place in Prolog?

问题描述

如果我在Prolog中有一个列表，例如X = [1、2、3、4]，如何将元素5添加到列表的末尾以使X = [1、2、3、4， 5]?

If I have a list in Prolog such as X = [1, 2, 3, 4], how do I add the element 5 to the end of the list to have X = [1, 2, 3, 4, 5]?

append函数需要两个列表，即append(A，B，C)才能将A和B连接到列表C.

The append function needs two lists, ie append(A,B,C) to get A and B concatenated to the list C.

我可以使用临时列表Y = [1,2,3,4]和Z = [5]来执行此操作，然后执行append(Y，Z，X)，但是我不喜欢使用临时列表.

I can do this with a temporary list Y = [1, 2, 3, 4] and Z = [5], to then do an append(Y, Z, X), but I don't like having a temporary list.

通常的免责声明在这里适用-这不是家庭作业，我只是在学习Prolog.

The usual disclaimers apply here - this is not homework and I am just learning Prolog.

推荐答案

Prolog中的变量只能分配一次.只要X的值为[1,2,3,4]，它就永远不会再有另一个值.就像您提到的，临时变量和append/3是实现此目的的方法.

Variables in Prolog can only be assigned once. As soon as X has the value [1,2,3,4] it can never have another value. A temporary variable and append/3, like you mentioned, is the way to do it.

话虽如此，您可以做一个可能不推荐的技巧.如果X = [1,2,3,4，Y]，则可以执行Y = 5，并且X现在具有所需的值.我相信这项技术称为差异列表.

Having said that, you can do one trick which probably isn't recommended. If X = [1,2,3,4,Y] then you can do Y=5 and X now has the value you want. I believe this technique is called a difference list.

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