c# - 构造类型、有界类型和无界类型的含义？

Question

来自 C# 5.0 规范

4.4 Constructed types

A generic type declaration, by itself, denotes an unbound generic type that is used as a “blueprint” to form many different types, by way of applying type arguments. The type arguments are written within angle brackets (< and >) immediately following the name of the generic type. An unbound generic type can only be used within a typeof-expression (§7.6.11). A type that includes at least one type argument is called a constructed type. A constructed type can be used in most places in the language in which a type name can appear. An unbound generic type can only be used within a typeof-expression (§7.6.11).
Constructed types can also be used in expressions as simple names (§7.6.2) or when accessing a member (§7.6.4).

“构造类型”的概念与“有界泛型”的概念相同吗？

4.4.3 Bound and unbound types

The term unbound type refers to a non-generic type or an unbound generic type. The term bound type refers to a non-generic type or a constructed type.

An unbound type refers to the entity declared by a type declaration. An unbound generic type is not itself a type, and cannot be used as the type of a variable, argument or return value, or as a base type. The only construct in which an unbound generic type can be referenced is the typeof expression (§7.6.11).

非泛型类型既是未绑定(bind)类型又是绑定(bind)类型吗？

Answer 1

Is the concept of "constructed type" the same as the concept of "bounded generic type"?

是的，模数你的错字。您的意思是说“绑定(bind)泛型类型”，而不是“绑定(bind)泛型类型”。

Is a non-generic type both an unbound and bound type?

是的。

Why are the terms so redundant/duplicate/convoluted?

这些术语是为了方便规范作者和编译器团队而发明的。您发现的唯一冗余是constructed 等于bound generic，这对我来说似乎很合理。我没有看到任何重复或卷积。

如果这些术语看起来很复杂，那么我向您提出，现代业务线 OO 语言的类型理论是一个复杂的主题；它的行话反射(reflect)了这种复杂性。

这样想可能会有所帮助。假设我们有一个 C 类，它接受 n 个类型参数，对于 n >= 0:

• 概念 C-that-takes-n-type-arguments 是一个未绑定(bind)类型。
• 概念 C-with-n-type-arguments 是一个绑定(bind)类型。
• 绑定(bind)的泛型类型必须是用类型参数构造的泛型类型，所以我们称它为构造类型。

显然，如果 n == 0，则 C 同时是绑定(bind)类型和未绑定(bind)类型。