在集合F＃中创建集合

Question

说我有一个空集。我想在该集合中创建多组字符串。我该怎么做呢？

例如，我正在尝试编写一个以Set<String*String>，Set<String>和Set<String>为参数的函数，并返回Set<Set<String>>。< / p>

type Country = string;;
type Chart = Set<Country*Country>;;
type Colour = Set<Country>;;
type Colouring = Set<Colour>;;

功能是：

let rec extColouring (chart: Chart) (colours : Colouring) (country : Country) =

该函数的值应为：

(*
val extColouring :
  chart:Chart -> colours:Colouring -> country:Country -> Set<Set<Country>>
*)

例如，图表就像

val myWorld : Chart =
  set
    [("Andorra", "Benin"); ("Andorra", "Canada"); ("Andorra", "Denmark");
     ("Benin", "Canada"); ("Benin", "Denmark"); ("Canada", "Denmark");
     ("Estonia", "Canada"); ("Estonia", "Denmark"); ("Estonia", "Finland");
     ...]