module Slot:sig..end
typet =Printexc.backtrace_slot
val is_raise : t -> boolis_raise slot is true when slot refers to a raising
      point in the code, and false when it comes from a simple
      function call.val location : t -> Printexc.location optionlocation slot returns the location information of the slot,
      if available, and None otherwise.
Some possible reasons for failing to return a location are as follow:
-g)val format : int -> t -> string optionformat pos slot returns the string representation of slot as
      raw_backtrace_to_string would format it, assuming it is the
      pos-th element of the backtrace: the 0-th element is
      pretty-printed differently than the others.
      Whole-backtrace printing functions also skip some uninformative
      slots; in that case, format pos slot returns None.
Since 4.02