[Haskell-beginners] Given a list of lists, how to drop the last item in each (sub)list.
peter.hall at memorphic.com
Thu Jan 2 12:11:31 UTC 2014
It's usually much simpler and better design to think about the simple case
first and then piece things together. So start with just modifying one
discardparitybyte :: [Bit] -> [Bit]
discardparitybyte xs = take 9 xs
When you're happy that this works, you can apply it to all the elements of
your data list:
discardallparitybytes :: [[Bit]] -> [[Bit]]
discardallparitybytes xs = map discardparitybye xs
And, if you want to, you can make it shorted by making the functions
discardparitybyte = take 9
discardallparitybytes = map discardparitybye
On 2 January 2014 11:38, Angus Comber <anguscomber at gmail.com> wrote:
> I have a list like this:
> The 'inner' list is a list of 9 items. I want to process the list so that
> a list of lists is returned but the 9th element in each inner list is
> So the function type would be [[a]] -> [[a]]
> So to get started I wrote a function like this:
> discardparitybyte :: [[Bit]] -> [[Bit]]
> But then not sure how to transform the inner list.
> I know I can access the first inner element using take 1 list. But how do
> I then access/manipulate this inner list?
> discardparitybyte (x:xs) = take 9 ??? (take 1 xs) : discardparitybyte ???
> Beginners mailing list
> Beginners at haskell.org
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