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undocumented - How to use Streaming package in v11.1?


I am trying to use the streaming package for lazy list operations demonstrated in this post. But I found that the package was significantly changed in version 11. After some observations, I found that LazyRange was moved to Streaming`ListAPI`Lazy`LazyRange, etc. However I encountered two problems in trivial tasks.



  1. Converting a lazy list to list. Leonid's post suggested Normal, which points to function Streaming`ListAPI`Eager`LazyListToList (this mapping is contained in Streaming`ListAPI`General`$StreamingAPIRegistry). Consider the following example:


ll = 2 # & /@ Streaming`ListAPI`Lazy`LazyRange[Infinity];
fl = Take[ll, 100];
(*part works correctly*)
fl[[10]]

(*20*)
Normal[fl]
(*long unexpected expression*)
Streaming`ListAPI`Eager`LazyListToList[fl]
(*same long unexpected expression*)


  1. Making a lazy tuple. I suppose it is similar(same) to Leonid's implementation here, however, both his example and ordinary syntax fail.


Streaming`ListAPI`Lazy`LazyTuples[{{1}, {2}}]

(*some uncaught errors*)

How to achieve the two tasks mentioned above?



Answer



The patch


Here is a way to get Streaming` working: on a fresh kernel execute the following:


Import["https://raw.githubusercontent.com/lshifr/StreamingPatch/master/StreamingPatchBootstrap.m"]

DownloadAndInstallStreamingPatch[]
Get["StreamingPatch`"]


If this worked, you should be able to use Streaming`. Note however, that the framework itself changed considerably. When time allows, I will try to provide some basic example of how it can be used.


Note also that while DownloadAndInstallStreamingPatch[] needs to be called only once (it installs the patch to your $UserBaseDirectory/ Applications), the Get["StreamingPatch`"] is needed to start every session with Streaming`.


Simple Tests


Here are a few simple tests to check that the patch worked (the patch loads Streaming` so one does not need to do that again, and actually should not).


ll = Streaming`LazyList`LazyListCreate[Range[100000], Byte[10000]]

Compute total:


Total @ ll


(*  5000050000 *)

A different way to do that:


Module[{sum = 0}, Scan[(sum += #) &, ll]; sum]

(*  5000050000 *)

Perform a chain of lazy transforms:


squared = Map[#^2 &, ll]
added = Map[# + 1 &, squared]

primes = Select[added, PrimeQ]

Convert to normal list:


Normal @ primes // Short

(*  {2,5,17,37,101,197,<<6645>>,9992001601,9995200577,9996800257,9998800037,9999200017} *)

Notes


Note that the patch has not been really tested more than very basic tests like the ones shown above. Please let me know if it does not work for you in some cases.


Note also, that Streaming` itself is undocumented functionality, for which there are no guarantees that it will not change in the future, or for that matter be present there at all. So use it at your own risk.



However, any feedback is very much appreciated.


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