anchor.diff:          <*> Piglet.Yield init.gender
           <*> Piglet.Yield init.comments
           <*> Piglet.Yield init.participates
  -        <*> Piglet.ManyInit init.friends "" (fun f ->
  -            Piglet.Yield f
  -            |> V.Is V.NotEmpty "A friend with no name?"
  -            |> NotANumber)
  +        <*> Piglet.ManyInit init.friends { firstName = ""; lastName = "" } Name
           |> Piglet.TransmitReader
           |> Piglet.WithSubmit
           |> Piglet.Run (fun u ->
  
positive.code: 
      [<JavaScript>]
      let User (firstName, lastName) age gender comments participates (friends: Many.Renderer<_,_,_>) liveUser submit =
          Div [
              Div [C.Input firstName |> RedBgOnError firstName |> C.WithLabel "First name:"]
              Div [C.Input lastName |> RedBgOnError lastName |> C.WithLabel "Last name:"]
              Div [C.Radio gender [Male, "Male"; Female, "Female"]]
              Div [C.IntInput age |> RedBgOnError age |> C.WithLabel "Age:"]
              Div [C.CheckBox participates |> C.WithLabel "Participate in the survey"]
              Div [C.TextArea comments |> C.WithLabel "Comments:"]
              Div [] |> C.RenderMany friends (fun ops friend ->
                  Div [
                      C.Input friend
                      C.Button ops.Delete -< [B [Text "Delete this friend"]]
                      C.ButtonValidate ops.MoveUp -< [Text "Move up"]
                      C.ButtonValidate ops.MoveDown -< [Text "Move down"]
                  ])
              Div [C.Button friends.Add -< [B [Text "Add a friend"]]]
              Table [
                  TBody [
                      TR [
                          TH [Attr.ColSpan "6"] -< [Text "Summary"]
                      ]
                      TR [
                          TH [Text "First name"]
  
negative.code:     type Gender = Male | Female
  
      type User =
          { name: Name; age: int; gender: Gender; comments: string; participates: bool; friends: Name[] }
  
          [<JavaScript>]
          static member Pretty u =
  