Session Types for Haskell

Latest on Hackage:2008.7.18

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GPL licensed by Matthew Sackman
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Session Types for Haskell. Allows the specification of communication protocols and then validation that an implementation does not violate said protocol. Ignore the build failure for hackage - it's just haddock being rubbish.


The most recent changes are at the top of this file.

2008 07 18

New multi receive variations:

plainMultiReceive takes a heterogeneous list of channel indexes
and a homogeneous list of functions. Basic operation is the same
as for multiReceive but should permit lists of channels which do
not have a statically determined length to be used. The trade off
is that every channel that is used must be of the same type.

combinedMultiRecv combines both the normal multiReceive and the
plainMultiReceive. This means that you should be able to have an
unbounded list of channels all of the same type (say, workers) and
then a few other channels which are statically known (say,
producers) and then multi receive amongst them all.

withChannelRec : this forces that the type of the pid overall has
not changed. Ideally should not be necessary, but seems to be useful
in some cases.

mapChannelsRec : this is like mapM: you supply a function and a list
of channel indexes and it will run the function over them all and
cons up the result. Thus every channel indicated should be of a type
which is compatible with the function.

2008 06 17

Multireceive now accepts channels where the next operation is offer.

Sends can be performed early - safely promoted over receives.

Support for testing asynchronously for non-blocking receives. Plus
with timeout options.

2008 05 12

Fixed a horrible bug that had meant that lists of fragment tuples
where more than one fragment was notDual were unusable. Was due to a
nasty interaction between type families and fundeps. Sort of.

Also now support subtyping on Pids. So you can now ssend a pid which
has a richer set of session type fragments than is listed in the
sendPid construct in the session type itself. The Pid is
automatically converted and everything works - the receiving party
(srecv) is limited to only using the session types as listed in the
sendPid / recvPid construct as you'd expect. Thus the session types
can become narrower and more accurate.

Also, some support for real network operations starting to
appear. Have a look at Control.Concurrent.Sessions.Network.Socket if
you're interested, along with Tests.TestNetwork.

2008 05 06

Added the Control.Concurrent.Session.SessionTypeMonad file that was

2008 05 02

Ensured that Pids carry around both dual and non-dual-ed session
types that they're prepared to start at. Before they were just
carrying non-dual-ed as this was all that was necessary for pairing
--> createSession.

A new and wonderful way of describing session types. This gets rid
of the old horrible absolute indexes and results in visually more
appealing and comprehensible session types.

Support for higher-order channels: you can now send channels over
channels, using sendChannel and recvChannel. Equivalent session type
descriptors are sendSession and recvSession.

Tidied up examples in Tests and Queens to demonstrate new features.

2008 04 02

Added smapM, smapM_, sjoin and fixed up tests file

2008 03 30

Added functions ssequence, ssequence_, withThenClose,
createSessionThenClose, forkThenClose

2008 03 29

Added scloseCh. Added additional type class constraints so that
creating, using and closing a channel doesn't alter the TyMaps.
Fixed a couple of other bugs. Pushed prog' into all Pids as well.

2008 03 25

Multi-receive is in and works and is pretty useful.

2008 03 24

Bug fixes. The public channel stuff is much more robust and you
can't now promote sends or receives early, which has forced me to
fix other bugs too. All good.

2008 03 23

Pid communication and the establishment of sessions based on known
Pids now works. This is basically public channels in and working.

2008 02 28

Interleaving appears. Type sigs get bigger. The night gets
darker. But it all works. One example so far using
interleaving. Need to deal properly with public channels and need to
write multi-recv.

2008 02 23

Added better examples to the Tests.hs module, including the standard
and much loved "calculator". Altered 'run' and '~||~' so that they
automatically add the necessary 'sjump's. Corrected some
documentation mistakes. Also corrected the fixity of ~>> and ~>>=.

2008 02 20

Completed rewrite. New version released to Hackage. Works correctly
in GHC 6.8.2. Now permits arbitrarily complex session types with
mixed branching and looping.
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