scalaz.effect

Duplicate a handle in the parent region.

A handle to a finalizer that allows you to duplicate it to a parent region using "dup". Duplicating a finalizer means that instead of being performed when the current region terminates, it is performed when the parent region terminates.

A mutable reference in the IO monad. Note that unsafePerformIO will allow leaking such a reference out of the monad, but any operations on a leaked reference are still monadic.

A monad transformer in which scarce resources can be opened. When the region terminates, all opened resources will be closed automatically. It's a type error to return an opened resource from the region, and no I/O with closed resources is possible.

Purely functional mutable state threads. Based on JL and SPJ's paper "Lazy Functional State Threads"

Mutable array in state thread S containing values of type A.

Mutable variable in state thread S containing a value of type A. http://research.microsoft.com/en-us/um/people/simonpj/papers/lazy-functional-state-threads.ps.Z

A safe alternative to the App trait in the Scala standard library. This trait provides an implementation of the main method by calling unsafePerformIO on a specified IO action.