Data.MonadicStreamFunction.Async

This module contains operations on monadic streams that are asynchronous, i.e. that change the speed at which data enters or leaves the MSF.

Documentation

concatS :: Monad m => MStream m [b] -> MStream m b

Concatenates a monadic stream of lists to a monadic stream. The stream of lists will be called exactly when new data is needed.

Example:

>>> let intstream = constS $ putStrLn "Enter a list of Ints:" >> readLn :: MStream IO [Int]
>>> reactimate $ concatS intstream >>> arrM print
Enter a list of Ints:
[1, 2, 33]
1
2
33
Enter a list of Ints:
[]
Enter a list of Ints:
[]
Enter a list of Ints:
[1, 2]
1
2
Enter a list of Ints:
...

Beware that concatS msf becomes unproductive when msf starts outputting empty lists forever. This is ok:

>>> let boolToList b = if b then ["Yes"] else []
>>> let everyOddEmpty = count >>> arr (even >>> boolToList)
>>> reactimate $ concatS everyOddEmpty >>> arrM print
"Yes"
"Yes"
"Yes"
"Yes"
"Yes"
...

But this will be caught in a loop:

>>> let after3Empty = count >>> arr ((<= 3) >>> boolToList)
>>> reactimate $ concatS after3Empty  >>> arrM print
"Yes"
"Yes"
"Yes"
^CInterrupted.