Re: [Haskell-beginners] print all days of calendar

I implemented the first step which works if I fix the months (instead of the Month Enum) and just return the day and not an element of type Date this works: calendar year = [ day | month <- [Jan, Feb], day <- [1..31], legalDate(day,month,year) == True ] this doesn't work: calendar year = [ Date(day,month,year) | month <- Month, day <- [1..31], legalDate(day,month,year) == True ] -------- Original-Nachricht --------

Datum: Sat, 19 Dec 2009 11:16:45 +0100 Von: "Chaddaï Fouché" An: kane96@gmx.de CC: beginners@haskell.org Betreff: Re: [Haskell-beginners] print all days of calendar

On Fri, Dec 18, 2009 at 5:01 PM, wrote:

...

I also have a function from a previous exercise which checks if a given date is valid. Is there a function for a loop that iterates from 1 to n and checks if the date is valid. If it's valid it should return the date otherwise it should jump to the next month or end at the end of the year? Or is it better to do it on another way with this data I have?

Since you derived Enum for Month, you can do [Jan..Dec] and get the list of the months in order. There are then two options, either you generate all cartesian product of [Jan..Dec] and [1..31] and check which are valid, or you write a function that for a given month and year tells you how many days it counts and then generate for month "m" all the pair in combination with [1..daysCount m].

Whatever your decision, list comprehensions are probably the tool of choice to do it though it is by no mean harder to do without.

-- Jedaï

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