Observation of monadic actions, including IO actions. Hooks to add observational capabilities for new base type and used defined types. Programmable browsing capabilities - structure browsers can by coded and plugged in. Includes a basic structure rendering package that uses a Haskell like syntax. Thread-safe observations are are supported.
Some versions support observations on exceptions.
It has been ported to the following systems. It should be straightforward to port to other Haskell compilers.