This project aims to be the Scala Incubator project for Automatic-Resource-Management in the scala library
SO
- Using flatMap is "ok" I think, if we trampoline
- I think having an applicative + traverse would be really nice. What do you need to make that happen?
I'm thinking of non/cats extension
is "zip" enough on managed resource?
I don't see zip in ManagedResource
I guess I'm looking for
and without flatMap
This is what I'm doing:
def sequenceManagedResources[R, T[X] <: TraversableOnce[X]](managedResources: T[ManagedResource[R]])(implicit canBuildFrom: CanBuildFrom[T[ManagedResource[R]], R, T[R]]): ManagedResource[T[R]] = {
val initialBuilderResource = unitManaged(canBuildFrom(managedResources))
val finalManagedBuilder = managedResources.foldLeft(initialBuilderResource) { case (builderResource, managedR) ⇒
builderResource.flatMap { builder ⇒
managedR.map(r ⇒ builder += r)
}
}
finalManagedBuilder.map(_.result())
}def unitManaged[T](value: => T): ManagedResource[T] = {
managed(()).map(_ ⇒ value)
}
so here's my lame impl: https://github.com/jsuereth/scala-arm/blob/master/src/main/scala/resource/package.scala#L57
and zip: https://github.com/jsuereth/scala-arm/blob/master/src/main/scala/resource/package.scala#L44 which would have the issue of stack overflow....
they may both have that issue....
for popping the stack, we'd need to use an alternative mechanism for this. I have an idea for how to do it, need to experiment
I like continuations
SO, what we should do here
is basically optimise for the "AbstractMangedResource" case
support was dropped in 2.11
i.e. as language features change, I wouldn't rely on that module
actually, looks like someone picked i tup
er picked it up
we removed it from ARM before that happened
@jsuereth @jsuereth_twitter , which account are you using?
Hi @jsuereth_twitter @jsuereth , would you mind changing
@Arty to @Atry in https://github.com/jsuereth/scala-arm/releases/tag/v2.0, please
@jsuereth_twitter You may remember that we talked a while ago about how to sequence lots of ManagedResources without getting a stack overflow on calling .acquireAndGet. We discussed the possibility of continuations. I've been wondering whether it could be done more easily. Have you thought about the problem since at all?
Oh I see that that conversation is just a few lines up
@jsuereth I've made a prototype of ManagedResource which does flatMap while avoiding big stacks of
trys for closing resources. Could you tell me what you think? I understand that it's nicer to hide the closing of a resource from other resources, but I can't see any other way to do this other than using continuations. https://gist.github.com/anonymous/32e847129948b84e622e715cecd4ff6b