Thanks for the feedback. I agree that newtype stuffs can be discussed
in another proposal. Let's focus on the package unix now.
I agree with most of your suggestion except the name
newProcessGroup[For]. I would rather only introduce
createProcessGroupFor and deprecate createProcessGroup for following
reasons:
(1) "create" seems to be more consistent than "new" with the rest of
the API; there is "createSession" and the committed patch in trac
#3994 is using the flag create_group.
(2) People who really want the new functionality of createProcessGroup
can just write createProcessGroupFor =<< getProcessID. This expression
should be future-proof.
In summary here is the full list of proposed changes in the first stage:
getProcessGroupID => same
getProcessGroupIDOf => new
createProcessGroup => deprecated; will be changed in the future
createProcessGroupFor => same as the old createProcessGroup
joinProcessGroup => same
setProcessGroupID => deprecated; will be changed in the future
setProcessGroupIDOf => same as the old setProcessGroupID
The previous patches on the trac actually already preserved
setProcessGroupID and createProcessGroup for backward compatibility.
(Sorry that I did not mention this.) All the patches have been tested
and updated with better documentation.
Regards,
Favonia
On Wed, May 11, 2011 at 5:11 AM, Simon Marlow
On 04/05/2011 14:18, Favonia wrote:
I am proposing a POSIX process group API change in order to (1) make ProcessGroupID a newtype of CPid, and (2) make it possible to query the process group of an existing process.
The motivation is that currently there is no way to query a process group of an existing process, but it seems needed for a proper implementation for ticket #3994. Also it seems nice if the compiler can do distinguish ProcessGroupID from ProcessID, just like Fd from CInt.
We should not make ProcessGroupID a newtype, because execpt for Fd, none of the other types in this family are newtypes. If we want to make them all newtypes, that should be done in one pass with a separate proposal.
I suggest retaining more backwards compatibility:
- do not change setProcessGroupID yet: the functionality is already provided by joinProcessGroup. Instead just deprecate it.
- instead of changing createProcessGroup, add
newProcessGroup :: IO ProcessGroupID newProcessGroupFor :: ProcessId -> IO ProcessGroupID
and deprecate createProcessGroup.
- Sometime later, change setProcessGroupID to the new version and undeprecate it.
PS: Sorry but the patch to the package base is not fully tested, as I have not figured out the correct way to compile package base (even without the patch). However the patch to the package unix should work independently of the patch to the package base.
If you make patches, I'll test and commit at the end of the discussion period.
Cheers, Simon