Lisp中的照应条件的示例将是什么? [英] What would be an example of an anaphoric conditional in Lisp?

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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