sealed trait Eff[R, A] extends AnyRef
Effects of type R, returning a value of type A
It is implemented as a "Free-er" monad with extensible effects:
- the "pure" case is a pure value of type A
- the "impure" case is:
- a disjoint union of possible effects
- a continuation of type X => Eff[R, A] indicating what to do if the current effect is of type M[X]
this type is represented by the
Arrs
type
- the "impure applicative" case is:
- list of disjoint unions of possible effects
- a function to apply to the values resulting from those effects
The monad implementation for this type is really simple:
point
is Purebind
simply appends the binding function to theArrs
continuation
Important:
The list of continuations is NOT implemented as a type sequence but simply as a Vector[Any => Eff[R, Any]]
This means that various .asInstanceOf
are present in the implementation and could lead
to burns and severe harm. Use with caution!
Similarly the list of effects in the applicative case is untyped and interpreters for those effects are supposed to create a list of values to feed the mapping function. If an interpreter doesn't create a list of values of the right size and with the right types, there will be a runtime exception.
The Pure, Impure and ImpureAp cases also incorporate a "last" action returning no value but just used for side-effects (shutting down an execution context for example). This action is meant to be executed at the end of all computations, regardless of the number of flatMaps added on the Eff value.
Since this last action will be executed, its value never collected so if it throws an exception it is possible to print it by defining the eff.debuglast system property (-Deff.debuglast=true)
- See also
http://okmij.org/ftp/Haskell/extensible/more.pdf
- Alphabetic
- By Inheritance
- Eff
- AnyRef
- Any
- Hide All
- Show All
- Public
- All
Abstract Value Members
Concrete Value Members
-
final
def
!=(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
final
def
##(): Int
- Definition Classes
- AnyRef → Any
- def *>[B](fb: Eff[R, B]): Eff[R, B]
- def <*[B](fb: Eff[R, B]): Eff[R, A]
-
final
def
==(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
def
addLast(l: ⇒ Eff[R, Unit]): Eff[R, A]
add one last action to be executed after any computation chained to this Eff value
- def ap[B](f: Eff[R, (A) ⇒ B]): Eff[R, B]
-
final
def
asInstanceOf[T0]: T0
- Definition Classes
- Any
-
def
clone(): AnyRef
- Attributes
- protected[java.lang]
- Definition Classes
- AnyRef
- Annotations
- @native() @throws( ... )
-
final
def
eq(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
def
equals(arg0: Any): Boolean
- Definition Classes
- AnyRef → Any
-
def
finalize(): Unit
- Attributes
- protected[java.lang]
- Definition Classes
- AnyRef
- Annotations
- @throws( classOf[java.lang.Throwable] )
- def flatMap[B](f: (A) ⇒ Eff[R, B]): Eff[R, B]
- def flatten[B](implicit ev: =:=[A, Eff[R, B]]): Eff[R, B]
-
final
def
getClass(): Class[_]
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
def
hashCode(): Int
- Definition Classes
- AnyRef → Any
- Annotations
- @native()
-
final
def
isInstanceOf[T0]: Boolean
- Definition Classes
- Any
- def map[B](f: (A) ⇒ B): Eff[R, B]
-
final
def
ne(arg0: AnyRef): Boolean
- Definition Classes
- AnyRef
-
final
def
notify(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native()
-
final
def
notifyAll(): Unit
- Definition Classes
- AnyRef
- Annotations
- @native()
-
final
def
synchronized[T0](arg0: ⇒ T0): T0
- Definition Classes
- AnyRef
-
def
toString(): String
- Definition Classes
- AnyRef → Any
-
final
def
wait(): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long, arg1: Int): Unit
- Definition Classes
- AnyRef
- Annotations
- @throws( ... )
-
final
def
wait(arg0: Long): Unit
- Definition Classes
- AnyRef
- Annotations
- @native() @throws( ... )