cats-effect Resource is extremely handy for managing the lifecycle of stateful resources, for example database or queue connections. It gives a main interface of:
trait Resource[F[_], A] {
/** - Acquire resource
* - Run f
* - guarantee that if acquire ran, release will run, even if `use` is cancelled or `f` fails
This document aims to show and compare three alternatives for achieving polymorphism in Scala.
Additionally, when implementing the typeclass pattern in Scala,
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I have some data which has adjacent entries that I want to group together and perform actions on.
I know roughly that fs2.Pull can be used to "step" through a stream and do more complicated
logic than the built in combinators allow. I don't know how to write one though!
In the end we should have something like
def combineAdjacent[F[_], A](
shouldCombine: (A, A) => Boolean,
I was talking to a coworker recently about general techniques that almost always form the core of any effort to write very fast, down-to-the-metal hot path code on the JVM, and they pointed out that there really isn't a particularly good place to go for this information. It occurred to me that, really, I had more or less picked up all of it by word of mouth and experience, and there just aren't any good reference sources on the topic. So… here's my word of mouth.
This is by no means a comprehensive gist. It's also important to understand that the techniques that I outline in here are not 100% absolute either. Performance on the JVM is an incredibly complicated subject, and while there are rules that almost always hold true, the "almost" remains very salient. Also, for many or even most applications, there will be other techniques that I'm not mentioning which will have a greater impact. JMH, Java Flight Recorder, and a good profiler are your very best friend! Mea
FWIW: I (@rondy) am not the creator of the content shared here, which is an excerpt from Edmond Lau's book. I simply copied and pasted it from another location and saved it as a personal note, before it gained popularity on news.ycombinator.com. Unfortunately, I cannot recall the exact origin of the original source, nor was I able to find the author's name, so I am can't provide the appropriate credits.