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Add isLeapYear function #47

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Merged
merged 2 commits into from
Feb 14, 2017
Merged

Add isLeapYear function #47

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30298be
Add isLeapYear function
MichaelXavier Feb 14, 2017
94eca80
Roll back import ordering change
MichaelXavier Feb 14, 2017
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7 changes: 7 additions & 0 deletions src/Data/Date.purs
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Expand Up @@ -7,6 +7,7 @@ module Data.Date
, day
, weekday
, diff
, isLeapYear
, module Data.Date.Component
) where

Expand Down Expand Up @@ -76,6 +77,12 @@ diff :: forall d. Duration d => Date -> Date -> d
diff (Date y1 m1 d1) (Date y2 m2 d2) =
toDuration $ runFn6 calcDiff y1 (fromEnum m1) d1 y2 (fromEnum m2) d2

-- | Is this year a leap year according to the proleptic Gregorian calendar?
isLeapYear :: Year -> Boolean
isLeapYear y = (mod y' 4 == 0) && ((mod y' 400 == 0) || not (mod y' 100 == 0))
where
y' = fromEnum y

-- TODO: these could (and probably should) be implemented in PS
foreign import canonicalDateImpl :: Fn4 (Year -> Int -> Day -> Date) Year Int Day Date
foreign import calcWeekday :: Fn3 Year Int Day Int
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6 changes: 6 additions & 0 deletions test/Test/Main.purs
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Expand Up @@ -98,6 +98,12 @@ main = do
log "Check that diff behaves as expected"
assert $ Date.diff d2 d1 == Duration.Days 29.0

let unsafeYear = unsafePartial fromJust <<< toEnum
log "Check that isLeapYear behaves as expected"
assert $ not $ Date.isLeapYear (unsafeYear 2017)
assert $ Date.isLeapYear (unsafeYear 2016)


-- datetime ----------------------------------------------------------------

let dt1 = DateTime.DateTime d1 t1
Expand Down