C＃：与Lambda表达式递归函数 [英] C#: Recursive functions with Lambdas

问题描述

以下不会编译：

  Func键＆LT; INT，INT＆GT; FAC = N =＆GT; （正＆下; = 1）？ 1：N * FAC（N  -  1）;
 

  

局部变量FAC可能不
  在访问之前进行初始化

如何让一个递归函数与lambda表达式？

[更新]

下面也是，我发现有趣的阅读两个链接：

1. Eric利珀特的为什么一个递归拉姆达造成一定的分配错误？


2. 匿名递归在C＃

解决方案

功能这种特殊的风格是不是C＃支持为单行声明。你必须声明和定义分离成两行

  Func键＆LT; INT，INT＆GT; FAC = NULL;
FAC = N =＆GT; （正＆下; = 1）？ 1：N * FAC（N  -  1）;
 

The below does not compile:

Func<int, int> fac = n => (n <= 1) ? 1 : n * fac(n - 1);

Local variable 'fac' might not be initialized before accessing

How can you make a recursive function with lambdas?

[Update]

Here are also two links that I found interesting to read:

1. Eric Lippert's "Why does a recursive lambda cause a definite assignment error?"
2. Anonymous Recursion in C#

解决方案

This particular style of function is not supported by C# as a single line declaration. You have to separate out the declaration and definition into 2 lines

Func<int, int> fac = null;
fac = n => (n <= 1) ? 1 : n * fac(n - 1);

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