# Capabilities: Separate and contain effects of IO monad.

[ bsd3, generics, library, security ] [ Propose Tags ]

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, http://dx.doi.org/10.1017/S0956796808006758) and uses the compdata package for compositional data types.

## Modules

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