At Fri, 1 Jul 2011 09:39:32 +0400,
Eugene Kirpichov wrote:
Hi,
I'm rewriting timeplot to avoid holding the whole input in memory, and
naturally a problem arises:
How to represent large but finite streams and functions that process
them, returning other streams or some kinds of aggregate
Eugene Kirpichov wrote:
I'm rewriting timeplot to avoid holding the whole input in memory, and
naturally a problem arises:
How to represent large but finite streams and functions that process
them, returning other streams or some kinds of aggregate values?
Examples:
* Adjacent differences of
Plain old lazy lists do not allow me to combine multiple concurrent
computations, e.g. I cannot define average from sum and length.
2011/7/1 Heinrich Apfelmus apfel...@quantentunnel.de:
Eugene Kirpichov wrote:
I'm rewriting timeplot to avoid holding the whole input in memory, and
naturally a
Sure you can.
runningAverage :: Int - [Double] - [Double]
runningAverage n xs = let chunk = take n xs
in (sum chunk / length chunk) : runningAverage (tail xs)
Lazy lists are absolutely ideal for this purpose.
Regards,
Malcolm
On 1 Jul 2011, at 07:33, Eugene Kirpichov
I meant the average of the whole list - given a sumS and lengthS (S
for Stream), write meanS as something like liftS2 (/) sumS lengthS.
Or is that possible with lazy lists too?
(looks like arrows actually - which arrow is appropriate here?)
2011/7/1 Malcolm Wallace malcolm.wall...@me.com:
Sure
On Fri, Jul 1, 2011 at 12:21 PM, Eugene Kirpichov ekirpic...@gmail.com wrote:
I meant the average of the whole list - given a sumS and lengthS (S
for Stream), write meanS as something like liftS2 (/) sumS lengthS.
Or is that possible with lazy lists too?
Sure you can. Sum, length and mean
Alexey, your definition of mean does not look like liftS2 (/) sum
length - you have to manually fuse these computations.
I'm asking for a formalism that does this fusion automatically (and
guaranteedly).
2011/7/1 Alexey Khudyakov alexey.sklad...@gmail.com:
On Fri, Jul 1, 2011 at 12:21 PM,
On Fri, Jul 1, 2011 at 12:54 PM, Eugene Kirpichov ekirpic...@gmail.com wrote:
Alexey, your definition of mean does not look like liftS2 (/) sum
length - you have to manually fuse these computations.
Well it was fused for numerical stability
I'm asking for a formalism that does this fusion
Eugene Kirpichov wrote:
Plain old lazy lists do not allow me to combine multiple concurrent
computations, e.g. I cannot define average from sum and length.
I meant the average of the whole list - given a sumS and lengthS (S
for Stream), write meanS as something like liftS2 (/) sumS lengthS.
Thanks but I'm afraid that's still not quite what I'm looking for;
guess I'll have to define my desire by my implementation - so once
it's ready I'll show the result to cafe :)
2011/7/1 Alexey Khudyakov alexey.sklad...@gmail.com:
On Fri, Jul 1, 2011 at 12:54 PM, Eugene Kirpichov
From: Eugene Kirpichov ekirpic...@gmail.com
Subject: [Haskell-cafe] Patterns for processing large but finite
streams
To: Haskell Cafe haskell-cafe@haskell.org
Message-ID: banlktikdsvq2wv4wjr+qmuvksoav0kt...@mail.gmail.com
Content-Type: text/plain; charset=ISO-8859-1
Hi,
I'm
After the list discussion, I'm surprised nobody mentioned Max Rabkin/Conal
Elliott's blog posts on folds and zips.
http://squing.blogspot.com/2008/11/beautiful-folding.html
http://conal.net/blog/posts/enhancing-a-zip/
They develop a formalism for zipping functions on lists.
Iteratee's `zip` set
Hi,
You're right, reifying stream processing functions seems indeed the
way to go - and that looks even more like arrows :)
I thought of something like this:
data SP i o = Yield [o] (Maybe (Maybe i - SP i o))
Scalar functions like sum and length are just SP's that return a
single item in the
Eugene Kirpichov ekirpic...@gmail.com writes:
2011/7/1 Heinrich Apfelmus apfel...@quantentunnel.de:
Eugene Kirpichov wrote:
I'm rewriting timeplot to avoid holding the whole input in memory, and
naturally a problem arises:
Plain old lazy lists?
Heretic! :-)
I generally have written a
This sound exactly like what attribute grammars, like the system
developed at Utrecht University [1], are useful for.
Erik
[1] http://www.cs.uu.nl/wiki/HUT/AttributeGrammarSystem
On Fri, Jul 1, 2011 at 10:54, Eugene Kirpichov ekirpic...@gmail.com wrote:
Alexey, your definition of mean does not
Hi,
I'm rewriting timeplot to avoid holding the whole input in memory, and
naturally a problem arises:
How to represent large but finite streams and functions that process
them, returning other streams or some kinds of aggregate values?
Examples:
* Adjacent differences of a stream of numbers
*
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