haskell - Haskell 中有哪些符号命名空间？

Question

我试图减少我对 Haskell 语法的困惑，并想了解 Haskell 中单独的命名空间是什么。

命名空间是指与编译器管理的各种符号表相对应的语法命名空间，而不是代码中定义的名称范围。

例如:

值名称(如函数名称)

数据构造函数

类型构造函数

类型参数(在类型定义中)

实例？

...？

我之所以感兴趣，是因为我在阅读 Haskell 代码时遇到了问题(肯定比任何其他语言都多)，因为我经常很难弄清楚我到底在看什么(尤其是数据/类型构造函数/类型声明)。

Haskell 似乎在许多地方重用了一些句法结构(尤其是 <name> <name> ... )并依赖于上下文 - 结果证明编译器在这方面比我好得多......

Answer 1

The Haskell Report §1.4 says

There are six kinds of names in Haskell: those for variables and constructors denote values; those for type variables, type constructors, and type classes refer to entities related to the type system; and module names refer to modules. There are two constraints on naming:

1. Names for variables and type variables are identifiers beginning with lowercase letters or underscore; the other four kinds of names are identifiers beginning with uppercase letters.
2. An identifier must not be used as the name of a type constructor and a class in the same scope.

These are the only constraints; for example, Int may simultaneously be the name of a module, class, and constructor within a single scope.