Re: [Haskell-beginners] find element of tupels

-------- Original-Nachricht --------

Datum: Thu, 17 Dec 2009 20:44:34 +0100 Von: "Henk-Jan van Tuyl" An: kane96@gmx.de, beginners@haskell.org Betreff: Re: [Haskell-beginners] find element of tupels

On Thu, 17 Dec 2009 17:18:41 +0100, wrote:

...

thanks Magnus, great, works so far. I added to check that myDay have to be greater 0:

legalDate :: Date -> Bool legalDate (myDay, myMonth, myYear) = maybe False id $ do days <- lookup myMonth monthAndMaxDay return (not (myDay <= 0) && (myDay <= days))

Another thing is, that I have to check for leapYears. I have a function that checks if a year is a leap year

isLeapYear :: Int -> Bool isLeapYear year = mod year 4 == 0

That is not entirely correct; from package time: isLeapYear :: Integer -> Bool isLeapYear year = (mod year 4 == 0) && ((mod year 400 == 0) || not (mod

year 100 == 0))

ok

...

monthAndMaxDay has 30 days for February which have to be fix. So i have to check in legalDate if the year is a leap year. If so I have to check myDay in February for 29 days, otherwise for 28 days. How can I implement this to isLegalDate?

Use fromGregorianValid from package time.

but the problem is I shall implement it on my own in this exercise

Regards, Henk-Jan van Tuyl

-- http://Van.Tuyl.eu/ http://members.chello.nl/hjgtuyl/tourdemonad.html --

--

-- Jetzt kostenlos herunterladen: Internet Explorer 8 und Mozilla Firefox 3.5 - sicherer, schneller und einfacher! http://portal.gmx.net/de/go/chbrowser