Patai, I read your paper on Elerea. It wasn't easy :), but I think I got the
picture.
So I would have 2 questions :
I made a simple function which turns an infinite list into a signal :
fromList :: [a] -> SignalGen (Signal a)
fromList xs =
stateful xs tail >>= memo . fmap head
1) It does what I want, but is it the good way to do it?
2) Since the returned signal may be used in several places and since I
obtain it through the generic fmap (and not through an Elerea primitive), I
guessed I had to "memo" it instead of simply using "return". Did I guess
right?
3) Concerning the functionnality added by the Param implementation, I have
the impression that the same can be achieved through the use of an external
signal in Simple (*). Am I right? If so, why did you make the Param
alternative?
(*) (ext, sink) <- external 'a'
driver <- start $ someSigGen ext
sink 'b'
driver
sink 'c'
driver
sink 'd'
driver
etc...
2010/12/16 Patai Gergely
So in the result of (a >>= f), the first element is taken from the first element of applying f to the first element of a; the second element is the second element in the result of applying f to the second element of a; and so on. Off the top of my head I am not sure what this corresponds to in terms of agents or where it would be useful, but I'm sure it must correspond to something interesting. In short, join corresponds to continuously sampling a stream of streams. In other words, it turns a higher-order stream into a dynamic data-flow network. That's exactly what the Elerea library [1] is good for: it allows you to do this in constant time instead of the quadratic cost of the pure implementation, but it forces you to traverse streams sequentially -- fortunately, that's exactly what you want to do most of the time. There is also a paper behind the library, which might help a bit in getting a clearer picture [2] (the paper also has an updated version in the process of being published).
Gergely
[1] http://hackage.haskell.org/package/elerea [2] http://sgate.emt.bme.hu/documents/patai/publications/PataiWFLP2010.pdf
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