Tracelog
A function that behaves like printf.
type 'a log = 'a printf -> unit
A log message takes a printf function and print with it. This avoid the need to parse and evaluate arguments when we do not log.
val set_verbosity_level :
[ `Result | `Error | `Warning | `Feedback of int | `Trace | `Debug ] ->
unit
Verbosity level, from less to most verbose. Default is to display everything below `Warning. Feedback levels are from less to more verbose (normal levels are from 0 to 2, but you can pass bigger numbers.)