[Haskell-beginners] consing an element to a list inside a file
kane96 at gmx.de
kane96 at gmx.de
Thu Feb 18 18:25:18 EST 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 --------
> Datum: Fri, 12 Feb 2010 23:18:06 +0100
> Von: Daniel Fischer <daniel.is.fischer at web.de>
> An: kane96 at gmx.de
> CC: beginners at haskell.org
> Betreff: Re: [Haskell-beginners] consing an element to a list inside a file
> Am Freitag 12 Februar 2010 20:15:26 schrieb kane96 at 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
> > 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,
> 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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