Type Members

1.  final class STM[+E, +A] extends AnyVal

   STM[E, A] represents an effect that can be performed transactionally, resulting in a failure E or a value A.

   STM[E, A] represents an effect that can be performed transactionally, resulting in a failure E or a value A.

   def transfer(receiver: TRef[Int],
                sender: TRef[Int], much: Int): UIO[Int] =
     STM.atomically {
       for {
         balance <- sender.get
         _       <- STM.check(balance >= much)
         _       <- receiver.update(_ + much)
         _       <- sender.update(_ - much)
         newAmnt <- receiver.get
       } yield newAmnt
     }
   
     val action: UIO[Int] =
       for {
         t <- STM.atomically(TRef.make(0).zip(TRef.make(20000)))
         (receiver, sender) = t
         balance <- transfer(receiver, sender, 1000)
       } yield balance

   Software Transactional Memory is a technique which allows composition of arbitrary atomic operations. It is the software analog of transactions in database systems.

   The API is lifted directly from the Haskell package Control.Concurrent.STM although the implementation does not resemble the Haskell one at all. http://hackage.haskell.org/package/stm-2.5.0.0/docs/Control-Concurrent-STM.html

   STM in Haskell was introduced in: Composable memory transactions, by Tim Harris, Simon Marlow, Simon Peyton Jones, and Maurice Herlihy, in ACM Conference on Principles and Practice of Parallel Programming 2005. https://www.microsoft.com/en-us/research/publication/composable-memory-transactions/

   See also: Lock Free Data Structures using STMs in Haskell, by Anthony Discolo, Tim Harris, Simon Marlow, Simon Peyton Jones, Satnam Singh) FLOPS 2006: Eighth International Symposium on Functional and Logic Programming, Fuji Susono, JAPAN, April 2006 https://www.microsoft.com/en-us/research/publication/lock-free-data-structures-using-stms-in-haskell/

2.  final class TPromise[E, A] extends AnyVal
3.  class TQueue[A] extends AnyRef
4.  class TRef[A] extends AnyRef

   A variable that can be modified as part of a transactional effect.

5.  final class TSemaphore extends AnyVal