C# 和 F# lambda 表达式代码生成

发布于 2024-09-03 21:00:27 字数 1262 浏览 4 评论 0原文

让我们看一下由 F# 为简单函数生成的代码：

let map_add valueToAdd xs =
    xs |> Seq.map (fun x -> x + valueToAdd)

生成的 lambda 表达式（F# 函数值的实例）代码将如下所示：

[Serializable]
internal class map_add@3 : FSharpFunc<int, int> {
    public int valueToAdd;
    internal map_add@3(int valueToAdd) { this.valueToAdd = valueToAdd; }
    public override int Invoke(int x)  { return (x + this.valueToAdd); }
}

并查看几乎相同的 C# 代码：

using System.Collections.Generic;
using System.Linq;

static class Program {
    static IEnumerable<int> SelectAdd(IEnumerable<int> source, int valueToAdd) {
        return source.Select(x => x + valueToAdd);
    }
}

以及为 C# lambda 表达式生成的代码：

[CompilerGenerated]
private sealed class <>c__DisplayClass1 {
    public int valueToAdd;
    public int <SelectAdd>b__0(int x) { return (x + this.valueToAdd); }
}

所以我有一些问题：

为什么 F# 生成的类没有标记为 sealed？
既然 F# 不允许可变闭包，为什么 F# 生成的类包含 public 字段？
为什么 F# 生成的类有构造函数？它可以用公共字段完美地初始化...
为什么 C# 生成的类没有标记为 [Serializable]？此外，为 F# 序列表达式生成的类也变成了 [Serializable]，而为 C# 迭代器生成的类却没有。

原文

Let's look at the code, generated by F# for simple function:

let map_add valueToAdd xs =
    xs |> Seq.map (fun x -> x + valueToAdd)

The generated code for lambda expression (instance of F# functional value) will looks like this:

[Serializable]
internal class map_add@3 : FSharpFunc<int, int> {
    public int valueToAdd;
    internal map_add@3(int valueToAdd) { this.valueToAdd = valueToAdd; }
    public override int Invoke(int x)  { return (x + this.valueToAdd); }
}

And look at nearly the same C# code:

using System.Collections.Generic;
using System.Linq;

static class Program {
    static IEnumerable<int> SelectAdd(IEnumerable<int> source, int valueToAdd) {
        return source.Select(x => x + valueToAdd);
    }
}

And the generated code for the C# lambda expression:

[CompilerGenerated]
private sealed class <>c__DisplayClass1 {
    public int valueToAdd;
    public int <SelectAdd>b__0(int x) { return (x + this.valueToAdd); }
}

So I have some questions:

Why is F#-generated class not marked as sealed?
Why does F#-generated class contain public fields since F# doesn't allow mutable closures?
Why does F# generated class have a constructor? It may be perfectly initialized with the public fields...
Why is C#-generated class not marked as [Serializable]? Also classes generated for F# sequence expressions also became [Serializable] and classes for C# iterators do not.