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import Data.List.Split
import Data.Time.Calendar;
import Data.Time.Calendar.Compat;
import Data.Time.Calendar.Julian;
import Text.Printf

printMonth :: Integer -> Int -> IO ()
printMonth year month = printWeeks entriesInMonth
    where
        -- printWeeks chunks the month's entries into weeks & prints each week on a new line
        printWeeks days = mapM_ (putStrLn.unwords) (chunksOf 7 days)

        -- entriesInMonth concatenates the empty entries at the start of the month with the days
        entriesInMonth = startPadding ++ daysOfMonth

        -- daysOfMonth generates a list of days of the month as strings
        daysOfMonth = map (printf "%2d") [1..(julianMonthLength year month)]

        -- startPadding generates blank strings for each empty entry before day '1'
        startPadding = replicate blanksBeforeDay1 "  "

        -- blanksBeforeDay1 is the number of empty entries before day '1'
        blanksBeforeDay1 = (fromEnum $ dayOfWeek (fromJulian year month 1)) `mod` 7

> printMonth 2019 12
                   1
 2  3  4  5  6  7  8
 9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31
> printMonth 20190 12
                1  2
 3  4  5  6  7  8  9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31
> printMonth 20190 11
          1  2  3  4
 5  6  7  8  9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30

Jörgen Andersson wrote:

shouldn't it be Data.Time.Calendar.Gregorian instead of Data.Time.Calendar.Julian

import Data.List.Split
import Data.Time.Calendar;
import Data.Time.Calendar.Compat;
import Text.Printf

printMonth :: Integer -> Int -> IO ()
printMonth year month = printWeeks entriesInMonth
    where
        -- printWeeks chunks the month's entries into weeks & prints each week on a new line
        printWeeks days = mapM_ (putStrLn.unwords) (chunksOf 7 days)

        -- entriesInMonth concatenates the empty entries at the start of the month with the days
        entriesInMonth = startPadding ++ daysOfMonth

        -- daysOfMonth generates a list of days of the month as strings
        daysOfMonth = map (printf "%2d") [1..(gregorianMonthLength year month)]

        -- startPadding generates blank strings for each empty entry before day '1'
        startPadding = replicate blanksBeforeDay1 "  "

        -- blanksBeforeDay1 is the number of empty entries before day '1'
        blanksBeforeDay1 = (fromEnum $ dayOfWeek (fromGregorian year month 1)) `mod` 7

Stuart Dootson wrote:

Being able to use Data.Time.Calendar rather than Data.Time.Calendar.Julian should have been a giveaway, shouldn't it

#!/bin/sh

cal

Nelek wrote:

each time I flight to my family I get blocked by Mocosoft