通用Lisp类层次结构 [英] Common Lisp class hierarchy

问题描述

Greg Pfeil的类层次结构图提供了通用的全面图Lisp类型系统。但是，我试图更好地理解层次结构顶部的类关系。举一个简单的例子，让（破坏人的名字年龄），然后让（defparameter * p1 *（make-person：name Yosh：age 19）。现在

Greg Pfeil's Class Hierarchy diagram provides a comprehensive picture the Common Lisp type system. But I'm trying to better understand the class relationships at the top of the hierarchy. For a simple example, let (defstruct person name age), and then (defparameter *p1* (make-person :name "Yosh" :age 19). Now

(typep *p1* 'person)
T
(typep *p1* 'structure)
T
(typep *p1* 'structure-object)
T
(typep *p1* 'atom)
T
(typep *p1* t)
T

1. Hyperspec 表示结构对象本身就是 t 。
   是 atom 和结构不是层次结构中的类型？

1. The Hyperspec says the precedence list for structure-object is only itself and t. Are atom and structure not types in the hierarchy?

的所有直接子类型是什么code> t ？更一般地说，如何检索任何给定类型的所有直接子类型或超类型（没有反复试验的 subtypep ）？或者，是否有一种方法可以遍历所有类型的列表？MOP是否提供函数来获取所有子类-/ super-classes？

What are all the direct subtypes of t? More generally, how can you retrieve all the direct subtypes or supertypes of any given type (without trial-and-error subtypep)? Alternately, is there a way to iterate over a list of all types? Does the MOP offer functions to get at all sub-/super-classes?

与集合论类似，从理论上讲，似乎所​​有Common Lisp类型/类都可以细分为<$的两个子类。 c $ c> t ;即 standard-object （与 elements 相对应，其实例为数字3，字符串 abc，结构s1，方法m1，等等）和 standard-class （与 sets 对应的类 standard-object ，类 number ，类 structure-object 等）。如果这不是 t 的实际细分，那么原因是否与实际实现有关？例如，避免层次结构中的递归类关系？

By analogy with set theory, it would seem that all Common Lisp types/classes could theoretically be subdivided into two subclasses of t; namely, standard-object (corresponding to elements with instances like the number 3, the string "abc", the structure s1, the method m1, etc.), and standard-class (corresponding to sets with instances like the class standard-object, the class number, the class structure-object, etc.). If this is not the actual subdivision of t, does the reason have something to do with practical implementation; for example, avoiding recursive class relationships in the hierarchy?

推荐答案

类型和类是两回事。

不要混淆它们。

有些类型具有相应的类。大多数人没有。

Some types have corresponding classes. Most have not.

atom 是类型的名称，而不是类的名称。

atom is the name of a type, but not of a class.

CL-USER 18 > (find-class 'atom nil)
NIL

因为 atom 不是类，它不能在任何类优先级列表中。
因此， atom 不在 structure-object 的类优先级列表中。

Since atom is not a class, it can't be in any class precedence list. Thus atom is not in the class precedence list of structure-object.

类型结构是非标准的，不是ANSI CL定义的。

The type structure is non-standard and not defined by ANSI CL.

类型不在类优先级列表中，而是类。

Types are not in a class precedence list, classes are.

类型的接口：

• 创建类型-> DEFTYPE


• 是某种类型的东西吗？ -> TYPEP


• 一种类型是另一种类型的子类型吗？ -> SUBTYPEP


• 什么是某种类型？ -> TYPE-OF

• create a type -> DEFTYPE
• is something of a type? -> TYPEP
• is a type a subtype of another type? -> SUBTYPEP
• what is a type for something? -> TYPE-OF

基本上，您可以使用类型进行所有操作。

That's basically all you can do with types.

CLOS类具有相应的类型

CLOS函数和类优先级列表不

CLOS functions and class precedence lists don't work with types, but classes have corresponding types.

CL-USER 23 > (defclass bar () ())
#<STANDARD-CLASS BAR 40200A2413>

CL-USER 24 > (typep (make-instance 'bar) 'bar)
T

CL-USER 25 > (type-of (make-instance 'bar))
BAR

CL-USER 26 > (class-of (make-instance 'bar))
#<STANDARD-CLASS BAR 40200A2413>

CLOS适用于类。因此，在扩展的CLOS中，您可以要求子类和超类。但是不适用于子类型或超类型。

CLOS works with classes. Thus in an extended CLOS you can ask for subclasses and superclasses. But not for subtypes or supertypes.

历史记录：类型和CLOS

通用Lisp从CLtL1开始，没有类型，没有CLOS。

Common Lisp started in CLtL1 with types and no CLOS.

CLOS和CLOS类已在几年后添加。添加它们的方式是一些类型获得了相应的类，并且这些类具有了相应的类型。

CLOS and CLOS classes have been added years later. They have been added in such a way that some types got corresponding classes and such that classes have corresponding types.

Common Lisp允许定义类型使用类型说明符，例如 AND ， OR ， SATISFIES ，成员，否，...对于那些不存在相应的CLOS类的情况。

Common Lisp allows to define types using type specifiers like AND, OR, SATISFIES, MEMBER, NOT, ... For those no corresponding CLOS classes exist.

也有复合类型说明符，例如（整数0 100）。这些类型也没有相应的CLOS类。

There are also compound type specifiers like (integer 0 100). There are also no corresponding CLOS classes for those types.

CL-USER 31 > (deftype integer100 () '(integer 0 100))
INTEGER100

CL-USER 32 > (find-class 'integer100)

Error: INTEGER100 is not the name of a class

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