[Haskell-cafe] Newbie: Appending arrays?

[Dmitri O.Kondratiev]

I don't quite understand how Data.Array.Diff work.
I tried this:

> let arr = listArray (1,3) [1..3] :: DiffArray Int Int

then:
> replaceDiffArray arr [(1, 777)]
array (1,3) [(1,1),(2,777),(3,3)]
Why when replacing first element the second one changes?

and also trying to add 4-th element results in:
Prelude Data.Array.Diff> replaceDiffArray arr [(4, 444)]
array (1,3) [(1,1),(2,2),(3,3)]

It looks like replaceDiffArray can not be used to add new element to the end
of array?


Thanks,
Dima

On Thu, Jul 10, 2008 at 10:59 PM, Jefferson Heard <
jefferson.r.heard at gmail.com> wrote:

> Two questions.  How often does the array change, and how big does it
> get?  It may well be that you just copy it and take the hit, as
> that'll be cheaper (even in C, incidentally) than any other solution,
> if it's a short array or if the updates happen rarely.
>
> If not, try using Data.Array.Diff and replaceDiffArray.  This is
> usually fairly efficient for most applications.
>
> By the way, depending on the type of the data you're putting into
> these arrays, Data.ByteString might be a good choice as well.
>
> On Thu, Jul 10, 2008 at 12:12 PM, Felipe Lessa <felipe.lessa at gmail.com>
> wrote:
> > 2008/7/10 Dmitri O.Kondratiev <dokondr at gmail.com>:
> >> allows construct an array of a fixed size. How to add more elements to
> the
> >> array later?
> >
> > I can't really answer your question, however I bet that it would
> > require allocating another, bigger array and copying the old elements
> > over, at least from time to time. So you may want to take a look at
> > Data.Sequence[1], supporting O(1) append on both sides and (sort of)
> > O(log i) for accessing the i-th element.
> >
> > [1]
> http://www.haskell.org/ghc/docs/latest/html/libraries/containers/Data-Sequence.html
> >
> > HTH,
> >
> > --
> > Felipe.
> > _______________________________________________
> > Haskell-Cafe mailing list
> > Haskell-Cafe at haskell.org
> > http://www.haskell.org/mailman/listinfo/haskell-cafe
> >
>
>
>
> --
> I try to take things like a crow; war and chaos don't always ruin a
> picnic, they just mean you have to be careful what you swallow.
>
> -- Jessica Edwards
>
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