t′a之间的任何差值都应与t′a之间的差值相同.和"F#中的t"? [英] Any difference between t<'a> and 'a t in F#?
问题描述
F#中的t<'a>和'a t的含义是否有区别?即使声明后也可以互换使用吗?
Is there any difference in meaning between t<'a> and 'a t in F#? Can they be used interchangeably even after declaration?
推荐答案
没有区别，是的，即使在声明后也可以互换使用.
There is no difference, and yes, they can be used interchangeably even after declaration.
But do note the F# Component Design Guidelines recommendation (Section 4.2):
考虑优先使用泛型(
Foo<T>)的前缀语法 后缀语法(T Foo)，具有四个显着例外(list，option，array，ref).
Consider using the prefix syntax for generics (
Foo<T>) in preference to postfix syntax (T Foo), with four notable exceptions (list,option,array,ref).
F#继承了后缀ML的两种命名方式
通用类型，例如"int list"以及前缀.NET样式，例如
"list<int>".您应该首选.NET样式，但以下四种除外
具体类型.对于F#列表，请使用后缀形式:"int list"
而不是"list<int>".对于选项，请使用后缀形式:"int option"
而不是"option<int>".对于数组，请使用语法名称
"int[]"而不是"int array"或"array<int>".对于refs，
使用"int ref"而不是"ref<int>"或"Ref<int>".对于其他所有
类型，请使用前缀形式:"HashSet<int>"，"Dictionary<string,int>"，
因为这符合.NET标准
F# inherits both the postfix ML style of naming
generic types, e.g. "int list" as well as the prefix .NET style, e.g.
"list<int>". You should prefer the .NET style, except for four
specific types. For F# lists, use the postfix form: "int list"
rather than "list<int>". For options, use the postfix form: "int option"
rather than "option<int>". For arrays, use the syntactic name
"int[]" rather than either "int array" or "array<int>". For refs,
use "int ref" rather than "ref<int>" or "Ref<int>". For all other
types, use the prefix form: "HashSet<int>", "Dictionary<string,int>",
since this conforms to .NET standards
此外，如果您使用ML样式的通用参数列表表示法(例如，)，则会收到编译器警告. ('a,'b) t与t<'a,'b>.
Also, you'll get a compiler warning if you use the ML-style generic parameter list notation, e.g. ('a,'b) t vs. t<'a,'b>.
And while we're at it, note the following recommendation in Section 3.1 of the same guide:
请在公共API中将PascalCase用作通用参数名称， 包括面向F#的库.特别是使用T，U， T1，T2用于任意通用参数，以及使用特定名称时 因此，对于面向F#的库，请使用诸如Key，Value和Arg之类的名称 (但不是TKey).
Do use PascalCase for generic parameter names in public APIs, including for F#-facing libraries. In particular, use names like T, U, T1, T2 for arbitrary generic parameters, and when specific names make sense, then for F#-facing libraries use names like Key, Value, Arg (but not e.g. TKey).
(尽管就我个人而言，我倾向于忽略面向F#的公共图书馆的建议).
(though personally I tend to ignore this recommendation for F#-facing public libraries).
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