Helper module for writing event loops that mesh with R events.

Events in R are dispatched from a number of file descriptors. The R runtime maintains a list of "input handlers", essentially a set of file descriptors together with callbacks for each one, invoked whenever the file descriptor becomes available for reading. This module exports functions for dispatching on both R events and Haskell events simultaneously, using GHC.Event, which is based on epollkqueuepoll under the hood for efficient and scalable event dispatching.

Event dispatching and processing is in particular necessary for R's GUI to be responsive. For a consistent user experience, you should arrange for all GUI related events to be dispatched from a single thread, ideally the program's main thread. In fact on some platforms, most notably OS X (darwin), you must use the main thread.

Event loops can be constructed in one of two ways:

1. eventLoopPoll, which uses GHC's poll(2) (and related syscalls) based efficient and scalable mechanisms for event dispatch;
2. eventLoopSelect, which uses R's select(2) based mechasism.

NOTE: in GHC 7.8 and 7.10, eventLoopPoll is currently unusable, due to a number of functions from the event API not being exported like they were previously.