commit 9f5e76ca88b1335b633c3543b1ec6a5655a6a189
parent 0f8c679a2a43df23ed3074466df048c173553831
Author: Byron Torres <b@torresjrjr.com>
Date: Sat, 8 Jan 2022 02:59:01 +0000
introduce martian time
Demonstrative code for Martian time for testing, probably should later
be moved to a third-party martian:: library.
Signed-off-by: Byron Torres <b@torresjrjr.com>
Diffstat:
3 files changed, 94 insertions(+), 3 deletions(-)
diff --git a/time/chrono/chronology.ha b/time/chrono/chronology.ha
@@ -11,4 +11,17 @@ export type moment = struct {
// 1970-01-01
export type epochal = i64;
+// The temporal length of a day on Earth.
+// Interpreted with an appropriate timescale like UTC, TAI, GPS.
export def EARTH_DAY: time::duration = 86400 * time::SECOND;
+
+// The following are temporary constants for demonstration of non-terrestrial
+// timescales, and should probably be moved to a third-party martian:: library.
+//
+// TODO: figure out a future-proof naming convention.
+
+// The temporal length of a solar day on Marth, in Martian seconds
+export def MARS_MARTIAN_SOL: time::duration = 86400 * time::SECOND;
+
+// The temporal length of a solar day on Marth, in Earth (SI) seconds
+export def MARS_TERRESTRIAL_SOL: time::duration = 88775.244147 * time::SECOND;
diff --git a/time/chrono/timescales.ha b/time/chrono/timescales.ha
@@ -95,7 +95,6 @@ fn conv_unix_tai(unix: time::instant) (time::instant | ambiguous | nonexistent)
};
-
// Global Positioning System Time
//
// Used for GPS coordination.
@@ -122,3 +121,64 @@ fn conv_gps_tai(gps: time::instant) (time::instant | ambiguous | nonexistent) =
return tai;
};
+
+// Terrestrial Time
+//
+// Used for astronomical timekeeping.
+// Based on TAI, with a constant offset.
+// Continuous (no leap seconds).
+export const TT: timescale = timescale {
+ to_tai = &conv_tt_tai,
+ from_tai = &conv_tai_tt,
+};
+
+def TT_OFFSET: time::duration = 32.184 * time::SECOND;
+
+fn conv_tai_tt(tai: time::instant) (time::instant | ambiguous | nonexistent) = {
+ const tt = time::instant {
+ sec = tai.sec + (TT_OFFSET / time::SECOND),
+ nsec = tai.nsec + (TT_OFFSET % time::SECOND),
+ };
+ return tt;
+};
+
+fn conv_tt_tai(tt: time::instant) (time::instant | ambiguous | nonexistent) = {
+ const tai = time::instant {
+ sec = tt.sec - (TT_OFFSET / time::SECOND),
+ nsec = tt.nsec + (TT_OFFSET % time::SECOND),
+ };
+ return tai;
+};
+
+
+// Coordinated Martian Time
+//
+// Used for local solar time on Mars.
+// Based on TT, with a constant factor.
+// Continuous (no leap seconds).
+export const MTC: timescale = timescale {
+ to_tai = &conv_mtc_tai,
+ from_tai = &conv_tai_mtc,
+};
+
+def FACTOR_TERRESTRIAL_MARTIAN: f64 = 1.0274912517;
+
+fn conv_tai_mtc(tai: time::instant) (time::instant | ambiguous | nonexistent) = {
+ // TODO: propagated ambiguous errors, how to reason about?
+ const tt = TT.from_tai(tai)?;
+ const mtc = time::instant {
+ sec = (tt.sec: f64 * FACTOR_TERRESTRIAL_MARTIAN): i64,
+ nsec = tt.nsec,
+ };
+ return mtc;
+};
+
+fn conv_mtc_tai(mtc: time::instant) (time::instant | ambiguous | nonexistent) = {
+ const tt = time::instant {
+ sec = (mtc.sec: f64 / FACTOR_TERRESTRIAL_MARTIAN): i64,
+ nsec = mtc.nsec,
+ };
+ // TODO: propagated ambiguous errors, how to reason about?
+ const tai = TT.to_tai(tt)?;
+ return tai;
+};
diff --git a/time/chrono/timezone.ha b/time/chrono/timezone.ha
@@ -95,7 +95,7 @@ const TZ_local: timezone = timezone {
transitions = [],
};
-// The UTC "Zulu" timezone
+// The UTC (Coordinated Universal Time) "Zulu" timezone
export const UTC_Z: *timezone = &TZ_UTC;
const TZ_UTC: timezone = timezone {
@@ -113,7 +113,7 @@ const TZ_UTC: timezone = timezone {
transitions = [],
};
-// The TAI "Zulu" timezone
+// The TAI (International Atomic Time) "Zulu" timezone
export const TAI_Z: *timezone = &TZ_TAI;
const TZ_TAI: timezone = timezone {
@@ -130,3 +130,21 @@ const TZ_TAI: timezone = timezone {
],
transitions = [],
};
+
+// The MTC (Coordinated Martian Time) "Zulu" timezone
+export const MTC_Z: *timezone = &TZ_MTC;
+
+const TZ_MTC: timezone = timezone {
+ name = "",
+ timescale = &MTC,
+ daylength = MARS_MARTIAN_SOL,
+ zones = [
+ zone {
+ zoffset = 0 * time::SECOND,
+ name = "Coordinated Martian Time",
+ abbrev = "MTC",
+ dst = false,
+ },
+ ],
+ transitions = [],
+};
