global-variables: Namespaced, global, and top-level mutable variables without unsafePerformIO.

[ bsd3, data, library, reflection ] [ Propose Tags ]

Data.Global provides a global namespace of IORefs, MVars and TVars. This namespace may be accessed in pure code. Yet reading and writing to those IORefs, MVars and TVars happens still in their respective monads.

Data.Global is designed to meet the following use cases:

  • Simplify the declaration of top-level mutable variables, by avoiding any pragmas as well as unsafePerformIO.

  • Avoid having to pass references explicitly throughout the program in order to let distant parts communicate.

  • Enable a communication by convention scheme, where e.g. different libraries may communicate without code dependencies.

  • Simplify the "configuration problem" - at least for code in the IO monad.

Note, that this library does not encourage sloppy software design by re-introducing all bad effects of global variables. Nevertheless, sometimes global variables are a suitable solution to a problem. In that case Data.Global simplifies and extends their handling significantly.

Examples are in the documentation of Data.Global.

Version History:

  1. 0.1.1: made compatible with stm-2.3

  2. 0.1.0: added declareEmptyMVar and widened the stm dependency

  3. 0: First public release




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Versions [RSS] 1.0,,
Dependencies base (>=4 && <5), containers (>=0.3 && <0.5), stm (>=2.1 && <2.4) [details]
License BSD-3-Clause
Copyright 2011, 2012 Jean-Marie Gaillourdet
Author Jean-Marie Gaillourdet and Patrick Michel
Maintainer Jean-Marie Gaillourdet <>
Category Data, Reflection
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Source repo head: hg clone
Uploaded by JeanMarieGaillourdet at 2012-03-03T09:25:25Z
Reverse Dependencies 2 direct, 0 indirect [details]
Downloads 2863 total (11 in the last 30 days)
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Status Docs uploaded by user
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