Why is this being removed? It's OK to add a new function if we need to, but removing the old one serves no purpose.

(Thought part of the point of this was to remove need for floats?)

On 29 June 2016 at 14:04, Thomas Leonard notifications@github.com wrote:

In unix/lib/time.mli
#168 (comment):

@@ -18,6 +18,6 @@ type +'a io = 'a Lwt.t

(** Timeout operations. *)

-val sleep : float -> unit Lwt.t

Why is this being removed? It's OK to add a new function if we need to,
but removing the old one serves no purpose.

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Richard Mortier
mort@cantab.net

@talex5 what is the purpose of keeping the function? my impression was that mirage-unix/xen is an implementation of (some of the modules defined in) mirage-types...

• It's used in lots of places and there's no need to break everything.
• OCaml uses floats to represent times, so having something that accepts OCaml times is useful.
• Using floats allows representing very long or short durations without errors.
• Using floats avoids error-prone scaling (e.g. all the * 1_000_000_000 magic constants in the recent patches).
• Using floats avoids overflow errors when converting between timebases (e.g. duration_at_freq_1 /. freq_1 *. freq_2 works; using int64 might not, depending on the frequencies and duration).

In general, it's conveniet, familiar and safe. So for code that doesn't care about performance, I'd prefer to stick to floats.

I just wrote up a durations library for easy conversion from your favourite time representation (microseconds, milliseconds, seconds, minutes, hours, years as int), seconds as floating point number) to nanoseconds (and the inverse). A uint64 representing nanoseconds allows for a range up to 584 years, that should be sufficient for sleep durations.

IMHO OCaml uses floats is a mistake (and the queued changes to PCLOCK/MCLOCK inside of mirage-types will get rid of this mistake inside of mirage).