stm: newBroadcastTChan and friends (a proposal, and a question)

[Edward Kmett]

+1

On May 13, 2013, at 1:24 AM, "wren ng thornton" <wren at freegeek.org> wrote:

> Hello all,
> 
> While looking through the pull requests for stm-chans I came across a
> discrepancy in the new stm. Namely, we have the following definitions:
> 
> * stm == 2.4
>    newBroadcastTChan :: STM (TChan a)
>    newBroadcastTChan = do
>        dummy_hole <- newTVar TNil
>        write_hole <- newTVar TNil
>        read <- newTVar dummy_hole
>        write <- newTVar write_hole
>        return (TChan read write)
> 
>    newBroadcastTChanIO :: IO (TChan a)
>    newBroadcastTChanIO = do
>        dummy_hole <- newTVarIO TNil
>        write_hole <- newTVarIO TNil
>        read <- newTVarIO dummy_hole
>        write <- newTVarIO write_hole
>        return (TChan read write)
> 
> * stm == 2.4.2
>    newBroadcastTChan :: STM (TChan a)
>    newBroadcastTChan = do
>        write_hole <- newTVar TNil
>        read <- newTVar (error ...)
>        write <- newTVar write_hole
>        return (TChan read write)
> 
>    newBroadcastTChanIO :: IO (TChan a)
>    newBroadcastTChanIO = do
>        dummy_hole <- newTVarIO TNil
>        write_hole <- newTVarIO TNil
>        read <- newTVarIO dummy_hole
>        write <- newTVarIO write_hole
>        return (TChan read write)
> 
> Thus, whoever changed the definition of newBroadcastTChan in 2.4.2 forgot
> to change newBroadcastTChanIO to keep it in sync.
> 
> PROPOSAL: I propose changing newBroadcastTChanIO to match
> newBroadcastTChan. (Deadline: 2 weeks)
> 
> 
> QUESTION: Is there any way to re-implement these functions using only the
> public API of version 2.3?
> 
> -- 
> Live well,
> ~wren
> 
> 
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