There seems to be a bug in the Channel module from
ghc-0.29.
If I understand the description in the paper
correctly, dupChan should allow two readers to
both read all the data passed along a channel.
This doesn't work because of the way the getChan
function is written.
It takes the next value from the read end hole, but
does not put it back into the MVar to allow any other
reader to access it.
The fix just requires one line:
getChan :: Chan a -> IO a
getChan (Chan read write)
= takeMVar read >>= \ rend ->
takeMVar rend >>= \ res@(ChItem val new_rend) ->
***putMVar rend res >>
putMVar read new_rend >>
return val
Cheers,
Meurig
