Prolog 类型检查 [英] Prolog type checking

问题描述

有没有办法确定 Prolog 中列表中元素的类型?我知道Prolog中没有明确输入变量，但我需要检查一个元素是否为数字、特定字符等.如何实现?

Is there a way to determine the type of an element within a list in Prolog? I know that variables aren't explicitly typed in Prolog, but I need to check whether an element is a number, a specific character, etc. How can this be accomplished?

推荐答案

Prolog 定义了一组用于类型测试的内置谓词:var/1, atom/1、integer/1、float/1、atomic/1、compound/1、nonvar/1、number/1，如果你知道该语言的数据类型，所有这些都具有不言自明的含义.对于特定字符，您可以在检查元素不是自由变量后利用与该字符的统一(否则统一总是成功的).

Prolog defines a group of built-in predicates for type testing purposes: var/1, atom/1, integer/1, float/1, atomic/1, compound/1, nonvar/1, number/1, all of them with quite a self-explanatory meaning if you know the data types of the language. For specific characters, you may exploit unification with that character, after checking that the element is not a free variable (otherwise unification is always successful).

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