Re: [Haskell-beginners] consing an element to a list inside a file

18 Feb 2010

      ok, now I did it by just calling from the original function by to a new one with an empty list at the beginning.

How can I add the date at the end of the list? By creating a new list from the new date and using concat or is there a simpler way?

-------- Original-Nachricht --------
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Datum: Fri, 12 Feb 2010 23:18:06 +0100
Von: Daniel Fischer 
An: kane96@gmx.de
CC: beginners@haskell.org
Betreff: Re: [Haskell-beginners] consing an element to a list inside a file
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Am Freitag 12 Februar 2010 20:15:26 schrieb kane96@gmx.de:
...
the exercise looks like that:
readMyCal :: IO MyCalendar
readMyCal = do putStr "day: "
               d <- readInt
               putStr "month: "
               m <- readMonth
               putStr "year: "
               y <- readInt
               let mydate = (d,m,y)
               if not (legalDate mydate) then
                   do putStrLn "wrong"
                   --COMPLETE-1--
               else
                   --COMPLETE-2--
COMPLETE-1: the user can give in a new date. I did it by simple calling
the function again
Reasonable.
...
COMPLETE-2: the user can choose if he wants to enter
a new. If not, all dates the user has put in should be put out as a
calendar (a list of dates)
Okay, that's not nice. But since you have no global variables to store the
list of dates entered in (yes, there are ways to have global variables,
but 
it's not a good idea unless you really have to), call
readMoreDates :: [MyDate] -> IO MyCaledar
readMoreDates previous = do ...
(code duplication where it isn't really necessary, but what the heck).
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Re: [Haskell-beginners] consing an element to a list inside a file

kane96＠gmx.de