raymondtay / JCConf_2019

Cats-Effect code repository for Java Community Conference 2019 @ Taipei, Taiwan

IO Monads in Scala

This repository is what i used for my talk on the IO Monad in Scala delivered in Taipei (Taiwan) @ October 2019. You can see the recording of my talk here.

For this talk, i have prepared 18 code examples where i hope to impress the readers (thats you ☺) that the IO monad should be your de-facto approach to solving your problems when using the functional programming libraries like Cats.

Code Examples

There are largely 3 categories of code snippets and its broken down as follows:

• Concurrent IO code which are either cancellable or not;
  • Examples that illustrate how to describe asynchronous, concurrent code which can describe error-handling;
• Concurrent modelling of data structures;
  • Buffered Channel and Skip Channel data structures are introduced and implemented; these structures were lifted from the paper _"Concurrent Haskell"
• Applications of the IO Monad;
  • Writer Monad integrated in an computation (e.g. Fibonacci sequence) and introducing the log4cats; the motivation is to demonstrate how the FP abstractions in cats integrate nicely into IO Monad
  • Modeled the Resource acquire-release mechanism around the http 1.x client provided by akka-http and readers can contrast the approach taken by http4s to see how regular things can be modeled into this approach

Run

You would need a JDK version 8 (at least) to run these examples; also, you would want to install Scala 2.12.x and sbt.

sbt:jcconf_2019> run
[warn] Multiple main classes detected.  Run 'show discoveredMainClasses' to see the list

Multiple main classes detected, select one to run:

 [1] async.cancellable.Beeper
 [2] async.cancellable.RacingNCancellable
 [3] async.cancellable.Sleeper
 [4] async.recovery.Mapper
 [5] cancellable.Fib
 [6] cancellable.FlatMaps
 [7] cancellable.MutualRecursion
 [8] cancellable.Snatcher
 [9] concurrent.BufferedChannel
 [10] concurrent.SkipChannnel
 [11] http.WebCrawlerAkkaHttp
 [12] http.WebCrawlerHttp4s
 [13] logging.FibLogger
 [14] logging.FibWriter
 [15] resources.ResourceAcquisitionRelease
 [16] stack.safe.Fib
 [17] uncancellable.Uncancellable1
 [18] uncancellable.Uncancellable2
[info] Packaging /Users/raymondtay/JCConf_2019/target/scala-2.12/jcconf_2019_2.12-0.1.0-SNAPSHOT.jar ...
[info] Done packaging.

Enter number: