Safe Haskell	Safe
Language	Haskell2010

Data.MonadicStreamFunction.Async

Description

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

Synopsis

Documentation

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

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 = arrM_ $ 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.