F#枚举类型约束的用例?

首先想到的是包装 System.Enum 使用强类型包装器:

// gets all underlying values for which an enum is defined
let definedVals<'a, 'b when 'a : enum<'b>> = 
  System.Enum.GetValues(typeof<'a>) 
  |> Seq.cast<'a> 
  |> Seq.map (LanguagePrimitives.EnumToValue)

let ints = definedVals<System.ConsoleColor,_>