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

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) -------- Original-Nachricht --------

Datum: Thu, 11 Feb 2010 23:30:05 +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

Am Donnerstag 11 Februar 2010 23:04:01 schrieb kane96@gmx.de:

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but the exercise was nearly complete on the sheet and I just have to complete two parts and one of them is to ask the user if he want's to do more input. If so, I have to let him input a new value (triple) for MyDatatype, otherwise I have to print the list with all triples

But to print it, you need to have a reference to the list of inputs. The easiest way is to have it as a parameter in the worker loop.

What *exactly* is your task? What is given and what are the specifications for a solution?

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Am Donnerstag 11 Februar 2010 22:34:45 schrieb kane96@gmx.de:

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the problem is the function should be readMyDatatype :: IO MyDatatype readMyDatatype = do ... Is it possible to do it somehow different without a parameter?

Separate the worker from the API function.

API:

readMyDatatype :: IO MyDatatype readMyDatatype = call worker with appropriate arguments

worker:

readMD :: t1 -> t2 -> ... -> tn -> IO MyDatatype

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