Question

type FooBar = FooBar with 
  static member print (a:FooBar) = printfn "%s" "foobar"

type PrintDefault = PrintDefault with
  static member inline print (a:int) = printfn "%s" "int"
  static member inline print (a:string) = printfn "%s" "string"

  static member inline print (a:obj) = printfn "%s" "object" // override others ?

let inline printOrDefault (a:^a, b:^b) =
  ((^a or ^b):(static member print: ^a -> unit) a)

let inline print a =
  printOrDefault (a, PrintDefault)

print 42
print "hello"
print FooBar
print (box 42)

选择方法不遵循最狭窄的原则吗？但是print : obj -> unit方法覆盖了其他方法。

public static void print<a>(a a)
{
    "Dynamic invocation of print is not supported";
    throw new NotSupportedException();
}

如果我不提供obj print，c#方法调用将获得NotSupportedException，如果我提供obj print，则f＃中的行为会混乱。

这里选择校长的方法是什么？

超越c＃interop，如果通过printOrDefault而非print调用，则事情是正确的。

print 42 // "object"
print "hello" // "object"
print FooBar // "object"
print (box 42) // "object"

printfn "----------------------------"

printOrDefault (42, PrintDefault) // "int"
printOrDefault ("hello", PrintDefault) // "string"
printOrDefault (FooBar, PrintDefault) // "foobar"
printOrDefault (box 42, PrintDefault) // "object"

f＃内联方法选择主要混淆

0 个答案: