Concurrent Sequential Processes
This library provides a concurrency framework based on the work of Tony Hoare in his book "Communicating Sequential Processes".
Usage
With CSP, your problem is modelled by processes that run concurrently, but are sequential internally. These processes communicate over channels, which provide a simple messaging API.
# Prints "Hello, World!" to stdout.
chan = CSP::Channel.new
CSP::Process.start { puts(chan.read) }
CSP::Process.start { chan << "Hello, World!" }
Note that the process is blocked when trying to read on the channel, and only resumes execution when it is able to read a value.