[commit: packages/time] format-widths, ghc, improve-leapseconds, master, posix-perf, tasty, wip/travis: Added fromMondayStartWeek and fromSundayStartWeek to Data.Time.Calendar.OrdinalDate. (04282fe)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/time

On branches: format-widths,ghc,improve-leapseconds,master,posix-perf,tasty,wip/travis
Link       : http://git.haskell.org/packages/time.git/commitdiff/04282fedbfbc79af60e7b430457f72789917da9d

>---------------------------------------------------------------

commit 04282fedbfbc79af60e7b430457f72789917da9d
Author: bjorn <bjorn at bringert.net>
Date:   Thu Nov 16 01:21:14 2006 -0800

    Added fromMondayStartWeek and fromSundayStartWeek to Data.Time.Calendar.OrdinalDate.
    
    I couldn't find any duals of mondayStartWeek and sundayStartWeek. They
    are useful when implementing parsing for %W and %U.
    
    darcs-hash:20061116092114-6cdb2-794a278759d65b1cdbb8fbb8f890409edbaa3834


>---------------------------------------------------------------

04282fedbfbc79af60e7b430457f72789917da9d
 Data/Time/Calendar/OrdinalDate.hs | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/Data/Time/Calendar/OrdinalDate.hs b/Data/Time/Calendar/OrdinalDate.hs
index a293b5e..a88943f 100644
--- a/Data/Time/Calendar/OrdinalDate.hs
+++ b/Data/Time/Calendar/OrdinalDate.hs
@@ -54,3 +54,36 @@ sundayStartWeek date =(fromInteger ((div d 7) - (div k 7)),fromInteger (mod d 7)
 	yd = snd (toOrdinalDate date)
 	d = (toModifiedJulianDay date) + 3
 	k = d - (toInteger yd)
+
+-- | The inverse of 'mondayStartWeek'. Get a 'Day' given the year,
+-- the number of the Monday-starting week, and the day of the week.
+-- The first Monday is the first day of week 1, any earlier days in the year 
+-- are week 0 (as \"%W\" in formatTime).
+fromMondayStartWeek :: Integer -- ^ Year.
+                    -> Int     -- ^ Monday-starting week number.
+                    -> Int     -- ^ Day of week. 
+                               -- Monday is 1, Sunday is 7 (as \"%u\" in formatTime).
+                    -> Day
+fromMondayStartWeek y w d = ModifiedJulianDay (firstDay + yd)
+    where yd = firstMonday + 7 * toInteger (w-1) + toInteger d - 1
+          -- first day of the year
+          firstDay = toModifiedJulianDay (fromOrdinalDate y 1)
+          -- 0-based year day of first monday of the year
+          firstMonday = (5 - firstDay) `mod` 7
+
+-- | The inverse of 'sundayStartWeek'. Get a 'Day' given the year and
+-- the number of the day of a Sunday-starting week.
+-- The first Sunday is the first day of week 1, any earlier days in the 
+-- year are week 0 (as \"%U\" in formatTime).
+-- Sunday is 0, Saturday is 6 (as \"%w\" in formatTime).
+fromSundayStartWeek :: Integer -- ^ Year.
+                    -> Int     -- ^ Sunday-starting week number.
+                    -> Int     -- ^ Day of week
+                               -- Sunday is 0, Saturday is 6 (as \"%w\" in formatTime).
+                    -> Day
+fromSundayStartWeek y w d = ModifiedJulianDay (firstDay + yd)
+    where yd = firstSunday + 7 * toInteger (w-1) + toInteger d
+          -- first day of the year
+          firstDay = toModifiedJulianDay (fromOrdinalDate y 1)
+          -- 0-based year day of first sunday of the year
+          firstSunday = (4 - firstDay) `mod` 7