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  > 1.0;;
  val it : float = 1.0

  > 1;;
  val it : int = 1

  > 3.0 + 1.0;;
  val it : float = 4.0

  > 3 + 1;;
  val it : int = 4

  > "3" + "4";;
  val it : string = "34"

  > 3.0 + 1;;

  3.0 + 1;;
  ------^

  stdin(5,7): error FS0001: The type 'int' does not match the type 'float'