热来宣布一个空的地图/字典？

Question

我想用Map初始化一个递归函数.要声明具有值的只读字典,我们可以这样做:

let dictionary1  = dict [ (1, "a"); (2, "b"); (3, "c") ]       

在线尝试!

现在,我想创建一个空字典.怎么实现呢？

我正在寻找像:

let dictionary1 = {} // <- ok this is js
let (stuff, dictionary2) = parseRec("whatever", dictionary1)

Answer 1

你可以做:

let dictionary1  = dict []

for elem in dictionary1 do
   printfn "Key: %d Value: %s" elem.Key elem.Value

这会给你一个空字典.

在printfn使用揭示的类型推理引擎的正确类型的键和值的.

如果您想要明确,那么您可以通过多种方式指定类型:

let dictionary1 = dict Seq.empty<int * string>
let dictionary1 = dict ([] : (int * string) list)
let dictionary1 = dict [] : System.Collections.Generic.IDictionary<int, string>
let dictionary1 : System.Collections.Generic.IDictionary<int, string> = dict []