ref: 264e4e6588d35226e110e08a92eae75295e962b9
parent: 15606f51c9d822f324ac97f3fc174a4e79414f00
author: Ori Bernstein <ori@eigenstate.org>
date: Thu Aug 28 11:24:36 EDT 2014
Remove a few magic constants.
--- a/lib/date/date.myr
+++ b/lib/date/date.myr
@@ -35,11 +35,9 @@
const diff : (a : date, b : date -> diff)
;;
-const monthbound = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 ]
-const leapmonthbound = [0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 ]
-const Day400y = (365*400 + 24*4 + 1)
-const Day100y = (365*100 + 24)
-const Day4y = (365*4 + 1)
+const Unix2Julian = 719468
+const Days400y = 365*400 + 4*25 - 3
+const Days4y = 365*4 + 1
const now = {-> utcnow()
@@ -79,19 +77,18 @@
/*
year, month, day:
- Implemented according to algorithm 199, conversions between calendar
- date and Julian day number:
- Robert G. Tantzen
- Air Force Missile: Development Center, Holloman AFB, New Mex.
+ Implemented according to "Algorithm 199, conversions between calendar
+ date and Julian day number", Robert G. Tantzen, Air Force Missile Development
+ Center, Holloman AFB, New Mex.
- Lots of magic.
+ Lots of magic. Yer a wizard, 'arry.
*/
- j = e + 719468
- y = (4 * j - 1) / 146097
- j = 4 * j - 1 - 146097 * y
+ j = e + Unix2Julian
+ y = (4 * j - 1) / Days400y
+ j = 4 * j - 1 - Days400y * y
d = j / 4
- j = (4 * d + 3) / 1461
- d = 4 * d + 3 - 1461 * j
+ j = (4 * d + 3) / Days4y
+ d = 4 * d + 3 - Days4y * j
d = (d + 4) / 4 ;
m = (5 * d - 3) / 153
d = 5 * d - 3 - 153 * m