Days between dates: Difference between revisions
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m (→{{header|Haskell}}: Added a variation (monadic composition in lieu of error handling)) |
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stringToDay date = parseTimeM True defaultTimeLocale "%Y-%-m-%-d" date</lang> |
stringToDay date = parseTimeM True defaultTimeLocale "%Y-%-m-%-d" date</lang> |
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{{out}} |
{{out}} |
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| ⚫ | |||
<pre> |
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There are |
There are 274 days between 2015-12-31 and 2016-09-30.</pre> |
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| ⚫ | |||
Or, composing rather than raising errors: |
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</pre> |
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<lang haskell>module Tokenized where |
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import Data.Time (Day) |
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import Data.Time.Calendar (diffDays) |
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import Data.Time.Format (defaultTimeLocale, parseTimeM) |
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-------------------- DAYS BETWEEN DATES ------------------ |
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daysBetween :: String -> String -> Maybe Integer |
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daysBetween s1 s2 = |
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dayFromString s1 |
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>>= ( \d1 -> |
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dayFromString s2 |
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>>= \d2 -> Just $ diffDays d2 d1 |
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) |
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dayFromString :: String -> Maybe Day |
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dayFromString = |
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parseTimeM |
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True |
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defaultTimeLocale |
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"%Y-%-m-%-d" |
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--------------------------- TEST ------------------------- |
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main :: IO () |
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main = |
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mapM_ |
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(putStrLn . uncurry showDateDiff) |
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[ ("2019-01-01", "2019-09-30"), |
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("2015-12-31", "2016-09-30") |
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] |
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showDateDiff :: String -> String -> String |
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showDateDiff xs ys = |
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maybe |
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( unlines |
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["Unparseable as date string pair:", xs, ys] |
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) |
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( \n -> |
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concat |
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["There are ", show n, " days between ", xs, " and ", ys, "."] |
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) |
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$ daysBetween xs ys</lang> |
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{{Out}} |
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<pre>There are 272 days between 2019-01-01 and 2019-09-30. |
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There are 274 days between 2015-12-31 and 2016-09-30.</pre> |
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=={{header|J}}== |
=={{header|J}}== |
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