The Capabilities package

[Tags:bsd3, library]

The capabilities library is an effort to make effects in Haskell more explicit by breaking the monolithic IO monad into smaller composable parts called capabilities: a use case might be an action that needs logging with current time but which should not be allowed any other IO. This exists as a pleasant middle ground between pure functions, the ST monad and the kitchen-sink IO providing a more fine-grained approach to effectful computations. Another benefit to this approach is security where a computation should only have access to resources requires to complete its job (principle of least privilege).

The implementation of the idea is based on Wouter Swierstra's Functional Pearl Data types a la carte (Journal of Functional Programming, 18(4):423-436, 2008, and uses the compdata package for compositional data types.


Dependencies base (==4.5.*), compdata (==0.6.*), directory (==1.1.*), free (==3.4.*), unix (==2.5.*) [details]
License BSD3
Author Baldur Blöndal, Daniel Schoepe
Category Security, Generics
Home page
Source repository head: git clone git://
Uploaded Thu Aug 8 09:31:24 UTC 2013 by BaldurBlondal
Distributions NixOS:
Downloads 465 total (13 in the last 30 days)
0 []
Status Docs not available [build log]
All reported builds failed as of 2016-10-24 [all 14 reports]
Hackage Matrix CI


  • Capabilities
    • Capabilities.IO
    • Capabilities.Internals
  • System
    • Environment
      • System.Environment.Capabilities


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