将C＃代码转换为F＃（如果声明）

问题描述：

我想知道如何逐行将此代码从C＃转换为F＃。我不想使用任何F＃的惯用法或类似用法。我试图了解如何直接映射 C＃的结构到F＃。

I'd like to know how to convert this code line by line from C# to F#. I am not looking to use any kind of F#'s idioms or something of the like. I am trying to understand how to map directly C#'s constructs to F#.

这是C＃代码：

//requires l.Length > 0
int GetMinimumValue(List<int> l) {
    int minVal = l[0];

    for (int i = 0; i < l.Length; ++i) {
        if (l[i] > minValue) {
            minVal = l[i];
        }
    }

    return minVal;
}

这是我的F＃尝试：

let getMinValue (l : int list) =
    let minVal = l.Head

    for i = 0 to (l.Length-1) do
        if (l.Item(i) > minVal) then
            minVal = col.Item(i)

    minVal

现在，这不起作用。问题似乎与 minVal = col.Item（i）行有关：

Now, this ain't working. The problem seems to be related with the minVal = col.Item(i) line:

This expression was expected to have type     unit     but here has type     bool

什么是

答

如果要逐行转换，请尝试以下操作

If you want to convert it line by line then try the following

let getMinValue (l:System.Collections.Generic.List<int>) =
  let mutable min = l.Item(0)
  for i = 0 to (l.Count-1) do
    if l.Item(i) < min then min <- l.Item(i)
  min

现在为什么您会收到该特定错误。看看下面的行

Now as to why you're getting that particular error. Take a look at the following line

minVal = col.Item(i)

在F＃中，这不是分配而是比较。因此，这是一个产生布尔值的表达式，但是在 for 循环内，所有表达式必须为 void / unit 返回。因此，您会收到一个错误。

In F# this is not an assignment but a comparison. So this is an expression which produces a bool value but inside the for loop all expressions must be void/unit returning. Hence you receive an error.

在F＃中，赋值我至少知道两种形式。

Assignment in F# has at least 2 forms that I am aware of.

// Assigning to a mutable value
let mutable v1 = 42
v1 <- 13

// Assigning to a ref cell
let v1 = ref 0
v1 := 42

当然，您应该绝对阅读Brian的文章。它非常详细，介绍了两种语言之间的翻译中的许多要点。

And of course, you should absolutely read Brian's article on this subject. It's very detailed and goes over many of the finer points on translating between the two languages

http://lorgonblog.spaces.live.com/Blog/cns!701679AD17B6D310!725.entry

http://lorgonblog.spaces.live.com/Blog/cns!701679AD17B6D310!725.entry

将C＃代码转换为F＃（如果声明）

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