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

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

Datum: Thu, 11 Feb 2010 22:54:59 +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 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

...

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

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Datum: Thu, 11 Feb 2010 21:41:15 +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 21:09:37 schrieb kane96@gmx.de:

...

mysecondlist = 0:mylist

that's was I was searching for, but how can I add the element to the same list?

You can't. When you add an element to a list, it's a different list.

...

I have to get any number of inputs from the user and at the end, if he doesn't want to make more inputs, I have to print a list with all the inputs he did.

Make the list a parameter of the input loop.

getInputs previous = do user <- getUserInput if endNow user then printList previous else getInputs (user:previous)

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