Readme for zeromq-haskell-0.8.1
This library provides Haskell bindings to zeromq (http://zeromq.org).
Current status
This software currently has beta status, i.e. it had seen limited testing.
Version 0.8.1 - zmqVersion has been renamed to version and reports the runtime version of 0MQ, instead of the compile time version macros.
Version 0.8.0 - zeromq-haskell can now be compiled either against 0MQ 2.x (default) or 0MQ 3.x.
Version 0.7.1 - Removes unix dependency
Verison 0.7.0 - Changes semantics of poll to return a list of the same length as it's parameter to allow identification of Sockets by index. PollEvent gets another constructor None to denote the absence of polling events.
Version 0.6.0 - This version renames "with" to "withContext" and introduces a new "withSocket" resource wrapper. The API is otherwise identical to 0.5.0
This software requires zeromq version 2.1.x.
Installation
As usual for Haskell packages this software is installed best via Cabal (http://www.haskell.org/cabal). In addition to GHC it depends on 0MQ of course. Please note that by default zeromq-haskell attempts to compile against 0MQ 2.x. If instead you want to use 0MQ 3.x, then provide the following flags to Cabal:
--flags="-zmq2 zmq3"
Notes
zeromq-haskell mostly follows 0MQ's API. One difference though is that sockets
are parameterized types, i.e. there is not one socket type but when creating a
socket the desired socket type has to be specified, e.g. Pair
and the
resulting socket is of type Socket Pair
.
This additional type information is used to ensure that only options applicable
to the socket type can be set, hence ZMQ_SUBSCRIBE
and ZMQ_UNSUBSCRIBE
which
only apply to ZMQ_SUB
sockets have their own functions (subscribe
and
unsubscribe
) which can only be used with sockets of type Socket Sub
.
Other differences are mostly for convenience. Also one does not deal directly with 0MQ messages, instead these are created internally as needed.
Examples
The test folder contains some simple tests mostly mimicking the ones that come with 0MQ.
Bugs
If you find any bugs or other shortcomings I would greatly appreciate a bug report, preferably via http://github.com/twittner/zeromq-haskell/issues or e-mail to toralf.wittner@gmail.com