Re: [Haskell-cafe] Newbie: Appending arrays?

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@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.

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2008/7/10 Dmitri O.Kondratiev :

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allows construct an array of a fixed size. How to add more elements to

On Thu, Jul 10, 2008 at 12:12 PM, Felipe Lessa wrote: the

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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-Sequen...

HTH,

-- Felipe. _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

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