什么是 Scheme 中的原子? [英] What are considered atoms in Scheme?

问题描述

有人可以向我解释或链接到任何可以帮助我理解原子是什么的有用资源(我在谷歌上找不到任何主题).

Can someone please explain or link me to any helpful resources ( I couldn't find any threads on google) that could help me understand what atoms are.

推荐答案

如今，我们将 atom 视为不是 cons-pair 且不为 null 的元素.这包括:

Nowadays we consider an atom an element that's not a cons-pair and that is not null. That includes:

• 数字
• 字符串
• 符号
• 布尔值
• 字符

最好通过以下程序来表达这一点，摘自 The Little Schemer 一书中:

This is best expressed with the following procedure, taken from the book The Little Schemer:

(define atom?
  (lambda (x)
    (and (not (pair? x)) (not (null? x)))))

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