A monad is an abstraction of the concept of sequencing of computations. A value of type 'a monad represents a computation that returns a value of type 'a.
return v returns the (trivial) computation that returns v.
ok_unit = return ()
try_with f catches exceptions thrown by
f and returns them in the Result.t as an
try_with_join is like
try_with, except that
f can throw exceptions or
Error directly, without ending up with a nested error; it is equivalent to
try_with f >>| Result.join.
extract_exn is passed along to
Monitor.try_with ?extract_exn and
specifies whether or not the monitor exn wrapper should be skipped (
or kept (