以下两个 Prolog 列表有什么区别? [英] What's the difference between following two Prolog lists?
问题描述
我对以下两个列表的差异感到困惑:
I'm kind of confused between the difference of the two following lists:
K = [1,2,3 | X].
和
K = [1,2,3,X].
布拉特科书中的问题其实是在conc的上下文中.
The question in the book of Bratko is actually in the context of conc.
浓度定义为:
conc([], L, L).
conc([X|L1], L2, [X|L3]) :- conc(L1, L2, L3).
现在的实际问题是是否在
The actual question now is if in
conc([1,2,3], [X], L2).
L2 与查询中的 K 是相同的列表 K = [1,2,3|X].
L2 is the same list as K in the query K = [1,2,3|X].
我不认为 L2 和 K 是一样的，但我不太确定如何解释.L2 是两个列表的串联.K 是我不确定的东西与可以由列表填充的变量 X 的串联...
I don't think L2 and K are the same, but I'm not so sure how to explain it. L2 is the concatenation of two lists. K is the concatenation of something I'm not sure of with a variable X that can be filled in by a list...
仍在学习 Prolog，如果这是一个愚蠢"的问题，请原谅我.
Still learning Prolog, so forgive me if this is a 'stupid' question.
推荐答案
在 Prolog 中，每个列表要么是空列表([])，要么是头尾([A | X]).Head 是第一个元素，tail 是列表的其余部分.
In Prolog each list is either empty list ([]) or head and a tail ([A | X]). Head is first element and tail is rest of the list.
示例:
[1]实际上是[1 |[]][1, 2]是[1 |[2 |[]]]- <代码>[1,2,3 |[4, 5]] 与
[1,2,3,4,5]相同(不同于 4 元素列表[1,2,3,[4,5]]).
[1]is actually[1 | []][1, 2]is[1 | [2 | []]][1,2,3 | [4, 5]]is the same as[1,2,3,4,5](which is different from 4-element list[1,2,3,[4,5]]).
所以在你的例子中 L2 是 [1,2,3,X]，它是最后一个元素 X 的四元素列表.同时 K 是 [1,2,3|X] 这是一个以 1,2,3 开头并且包含所有元素的列表X.
So in your example L2 is [1,2,3,X], which is four element list with last element X. Meanwhile K is [1,2,3|X] which is a lists which starts with 1,2,3 and than has all elements of X.
下图展示了[1,2,3,X]和[1,2,3|X]的结构区别.
Following picture shows the difference between structures of [1,2,3,X] and [1,2,3|X].
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