Doomsday rule: Difference between revisions
Add Haskell
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M= 2 D= 12 Y= 2077 DAY=FRIDAY
M= 4 D= 2 Y= 2101 DAY=SATURDAY</pre>
=={{header|Haskell}}==
<lang haskell>import Text.Printf
data Date = Date {year :: Int, month :: Int, day :: Int}
instance Show Date where
show (Date {year = y, month = m, day = d}) = printf "%2d/%2d/%4d" m d y
leap :: Int -> Bool
leap year = year`mod`4==0 && (year`mod`100/=0 || year`mod`400==0)
weekday :: Date -> Int
weekday (Date {year = y, month = m, day = d}) = (doom + d - anchor + 7) `mod` 7
where doom = (s + t + (t `div` 4) + c_anchor) `mod` 7
anchor = dooms !! pred m
c_anchor = (5 * mod c 4 + 2) `mod` 7
dooms = (if leap y then [4,1] else [3,7]) ++ [7,4,2,6,4,1,5,3,7,5]
(c, r) = y `divMod` 100
(s, t) = r `divMod` 12
days :: [String]
days = words "Sunday Monday Tuesday Wednesday Thursday Friday Saturday"
dates :: [Date]
dates = [ Date { year = 1800, month = 1, day = 6},
Date { year = 1875, month = 3, day = 29},
Date { year = 1915, month = 12, day = 7},
Date { year = 1970, month = 12, day = 23},
Date { year = 2043, month = 5, day = 14},
Date { year = 2077, month = 2, day = 12},
Date { year = 2101, month = 4, day = 2} ]
dateAndDay :: Date -> String
dateAndDay d = printf "%s: %s" (show d) (days !! weekday d)
main :: IO ()
main = putStr $ unlines $ map dateAndDay dates </lang>
{{out}}
<pre> 1/ 6/1800: Monday
3/29/1875: Monday
12/ 7/1915: Tuesday
12/23/1970: Wednesday
5/14/2043: Thursday
2/12/2077: Friday
4/ 2/2101: Saturday</pre>
=={{header|Julia}}==
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