Date Sorting...

David Feuer
Thu, 7 Mar 2002 21:06:17 -0500

On Thu, Mar 07, 2002, Michael Ruth wrote:
> Hello,
> I am pretty new to Functional programming, and I am having the following 
> problem.
> I need to sort a list of dates provided in an input file.  One date per 
> line.. day month year is the order. And each is represented by integers 
> seperated by spaces. And once the list is sorted output the results to a 
> file.
> I having trouble knowing where to start.  This is what I was thinking the 
> best line of attack was:

This actually sounds pretty reasonable (though I don't know whether
quicksort is best or not... maybe someone else can say).  To save
programming, you may want to use the lazy IO primitives, but I don't
particularly suggest it.  There is a function called map (defined in the
standard prelude) that you will probably find useful for one of these
steps.  Why don't you write this up and send it to the list so that we
can look at code rather than English text?

> --read in the lines one by one into a list
> --then iterate thru the list while breaking the strings into [Int] list
> -- of 3 elements [day,month,year]
> --then quicksort overall list
> --then print out overall list line by line
> I understand this is a imperative approach, but this is the way I was taught 
> how to program, well that and OOP. How do I go about writing this in a 
> functional sense ? And is there another way to do this AKA another plan of 
> attack ?. Thanks very much for your time and consideration.
> Michael
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