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:                         TD [] |> C.Show liveUser (function
                              | {comments = ""} -> [I [Text "(no comment)"]]
                              | {comments = c} -> [Span [Text c]])
                          TD [] |> C.ShowString friends.Output (String.concat ", ")
                      ]
                  ]
              ]
  
negative.code: 
      [<JavaScript>]
      let User (firstName, lastName) age gender comments participates (friends: Many.Renderer<_,_,_>) liveUser submit =
          let nameInput s =
              C.Input s |> RedBgOnError (s.Through liveUser)
          Div [
              Div [nameInput firstName |> C.WithLabel "First name:"]
              Div [nameInput lastName |> C.WithLabel "Last name:"]
              Div [C.Radio gender [Male, "Male"; Female, "Female"]]
              Div [C.IntInput age |> RedBgOnError (age.Through liveUser) |> 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 (first, last) ->
                  Div [
                      nameInput first
                      nameInput last
                      C.Button ops.Delete -< [B [Text "Delete this friend"]]
                      C.ButtonValidate ops.MoveUp -< [Text "Move up"]
                      C.ButtonValidate ops.MoveDown -< [Text "Move down"]
                  ])
                  |> C.WithLabel "Friends:"
              Div [C.Button friends.Add -< [B [Text "Add a friend"]]]
              Table [
                  TBody [
                      TR [
                          TH [Attr.ColSpan "7"] -< [Text "Summary"]
                      ]
                      TR [
                          TH [Text "First name"]
  