On Thu, Feb 17, 2011 at 6:21 PM, Henning Thielemann < lemm...@henning-thielemann.de> wrote:
> John Lato schrieb: > > > Does anyone know of a purely functional equivalent to a circular buffer? > > It depends on the application you have in mind. > For programming a constant delay of n samples of a lazy list including > feedback, > you can use a lazy list instead of a circular buffer. > For efficiency reasons you can use a chunky StorableVector with chunk > size up to n. > This is like rolling out the circular buffer to an infinite list. > > Something simple like > > let output :: [Double] > output = mix (input + delay n output) > > would work. > For a constant delay, one of the real-time queues would probably be better yet. A chunky StorableVector can work, but there's a lot of copying unless n is very small. If I use a Sequence for the mutating chunk and vectors for other chunks, it might work well. Sort of like a Builder. I'll try it and report back if I find anything interesting. But I'm really interested in long-ish (several seconds) delay lines with multiple varying taps. The other "brillant" idea I have involves reconfiguring queue lengths based upon lookups, similar to a splay tree. I may try to implement it but I would be surprised if get it right. > > > I'm looking for something that supports efficient insertion and lookup, > > and doesn't rely upon mutable data. I don't want to use mutable data > > because I'd like to embed this in CCA, which to my knowledge doesn't yet > > support Kleisli arrows. > > Embedding the above idea into an arrow that emits one output sample per > input sample would not work. Mutable arrays in the ST monad would help, > but this requires that the arrow is built around the ST monad. > Exactly, hence the problem using this with CCA at the moment.
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