如何在Lisp中定义这样的常量？ [英] How to define constant like this in lisp?

问题描述

在python中可以做到这一点

In python it's possible to do this

EMPTY, PAWN, KNIGHT, BISHOP, ROOK, QUEEN, KING, BPAWN = range(8)

您将如何做等同于Lisp的操作？

How would you do equivalent in lisp?

推荐答案

在Lisp中，仅使用符号会更加惯用。通常作为自评估关键字符号：

It would be more idiomatic in Lisp to just use symbols. Typically as self-evaluating keyword symbols:

(defparameter *chess-pieces*
  '(:EMPTY :PAWN :KNIGHT :BISHOP :ROOK :QUEEN :KING :BPAWN))

有定义数字值的原因-有时。尤其是当您需要与外部功能交谈时。在Lisp中，默认情况下将使用符号。

There are reasons to define numeric values - sometimes. Especially when you need to talk to foreign functions. In Lisp you would by default use symbols.

Common Lisp没有真正的枚举类型。与使用数字变量相比，以动态类型语言使用符号具有一些优势。例如，在调试期间，变量内容更具描述性：

Common Lisp does not have a real enumeration type. Using symbols in a dynamically typed language has some advantages over using numeric variables. For example during debugging the variable contents are more descriptive:

比较：

> (setf c4 queen)

> c4
6

vs。

> (setf c4 :queen)

> c4
:queen

在后一个示例中，符号值是自描述的。

In the latter example the symbol value is self-descriptive.

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