Lisp中的照应条件的示例将是什么?

问题描述

在Lisp中反指条件的示例将是什么?请也解释代码.

What would be an example of an anaphoric conditional in Lisp? Please explain the code as well.

推荐答案

一个例子是Common Lisp LOOP:

An example is the Common Lisp LOOP:

(loop for item in list
      when (general-predicate item)
      collect it)

变量IT具有测试表达式的值.这是ANSI Common Lisp LOOP工具的功能.

The variable IT has the value of the test expression. This is a feature of the ANSI Common Lisp LOOP facility.

示例:

(loop for s in '("sin" "Sin" "SIN")
      when (find-symbol s)
      collect it)

返回

 (SIN)

因为仅"SIN"是现有符号的名称，此处为符号SIN.在Common Lisp中，符号名称默认情况下内部具有大写名称.

because only "SIN" is a name for an existing symbol, here the symbol SIN. In Common Lisp symbol names have internally uppercase names by default.

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