Five weekends: Difference between revisions
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=={{header|Haskell}}== |
=={{header|Haskell}}== |
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====Without using date libraries==== |
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Not using any helper libraries, this code profits from Haskell's lazy evaluation. |
Not using any helper libraries, this code profits from Haskell's lazy evaluation. |
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Knowing that the first day of 1900 was a Monday, we make an infinit list of days and split it in years and months. |
Knowing that the first day of 1900 was a Monday, we make an infinit list of days and split it in years and months. |
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1900, 1906, 1917, 1923, 1928, 1934, 1945, 1951, 1956, 1962, 1973, 1979, 1984, 1990, 2001, 2007, 2012, 2018, 2029, 2035, 2040, 2046, 2057, 2063, 2068, 2074, 2085, 2091, 2096 |
1900, 1906, 1917, 1923, 1928, 1934, 1945, 1951, 1956, 1962, 1973, 1979, 1984, 1990, 2001, 2007, 2012, 2018, 2029, 2035, 2040, 2046, 2057, 2063, 2068, 2074, 2085, 2091, 2096 |
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</pre> |
</pre> |
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====Using Data.Time==== |
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<lang haskell>import Data.Time (Day, fromGregorian, gregorianMonthLength) |
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import Data.Time.Calendar.WeekDate (toWeekDate) |
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import Data.List.Split (chunksOf) |
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import Data.List (intercalate) |
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-- MONTHS WITH FIVE WEEKENDS -------------------------------------------------- |
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fiveFridayMonths :: Integer -> [(Integer, Int)] |
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fiveFridayMonths y = |
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[1 .. 12] >>= |
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(\m -> |
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[ (y, m) |
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| isFriday (fromGregorian y m 1) && gregorianMonthLength y m == 31 ]) |
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isFriday :: Day -> Bool |
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isFriday d = |
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let (_, _, day) = toWeekDate d |
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in day == 5 |
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-- TEST ----------------------------------------------------------------------- |
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main :: IO () |
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main = do |
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let years = [1900 .. 2100] |
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xs = fiveFridayMonths <$> years |
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lean = |
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concat $ |
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zipWith |
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(\a b -> |
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[ b |
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| null a ]) |
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xs |
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years |
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(putStrLn . intercalate "\n\n") |
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[ "How many five-weekend months 1900-2100 ?" |
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, '\t' : show (length . concat $ xs) |
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, "First five ?" |
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, '\t' : show (concat (take 5 xs)) |
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, "Last five ?" |
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, '\t' : show ((reverse . concat) (take 5 (reverse xs))) |
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, "How many lean years ? (No five-weekend months)" |
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, '\t' : show (length lean) |
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, "Which years are lean ?" |
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, unlines (('\t' :) <$> ((unwords . (show <$>)) <$> chunksOf 5 lean)) |
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]</lang> |
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{{Out}} |
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<pre>How many five-weekend months 1900-2100 ? |
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201 |
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First five ? |
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[(1901,3),(1902,8),(1903,5),(1904,1),(1904,7)] |
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Last five ? |
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[(2097,3),(2098,8),(2099,5),(2100,10),(2100,1)] |
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How many lean years ? (No five-weekend months) |
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29 |
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Which years are lean ? |
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1900 1906 1917 1923 1928 |
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1934 1945 1951 1956 1962 |
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1973 1979 1984 1990 2001 |
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2007 2012 2018 2029 2035 |
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2040 2046 2057 2063 2068 |
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2074 2085 2091 2096</pre> |
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=={{header|Inform 7}}== |
=={{header|Inform 7}}== |
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