module Trace: sig end
Debug module,
functions for trace and internal errors
exception Internal_error of string
raised for debug purpose to report an unexpected error,
other than an error in the input file.
val trace : ('a, unit, unit) format -> 'a
Print the given formatted message on the error output,
if trace mode is on. Otherwise do nothing.
val trace_on : unit -> unit
set trace mode on
val trace_off : unit -> unit
set trace mode off
val is_trace_mode : unit -> bool
Returns whether the trace mode is on