Real World Scalaz

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Real World Scalaz

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Real World Scalaz

  1. 1. REAL W⊛RLD SCALAZ http://speakerdeck.com/u/jrwest/p/real-world-scalazchanged talk title (“practical scalaz” by Chris Marshall http://skillsmatter.com/podcast/scala/practical-scalaz-2518)
  2. 2. “If you are thinking of using Scalaz, stop now while you still have your sanity"* context: java devs learning scala* source: http://zeroturnaround.com/blog/scala-sink-or-swim-part-1/#scalaz
  3. 3. “How does this help you ship features or improve your product?”* context: commenting on the use of lenses* source: https://twitter.com/#!/coda/status/167794305107361796)
  4. 4. “It will not immediately help you write better programs that are easy to understand”* hear/read this often* source: http://zeroturnaround.com/blog/scala-sink-or-swim-part-1/#scalaz
  5. 5. “There are two types of [libraries]: the ones people hate and the ones nobody uses” - unknown* applies to scala too* know correct attribution? contact me
  6. 6. HOW & WHY?* those quotes pretty much boil down to these two questions:* how: apply tools given by scalaz to real world problems? to handle human scale?* why would we choose this solution over other ones?
  7. 7. @_jrwest github.com/jrwest blog.loopedstrange.com* a little context before we talk about the “how & why?”
  8. 8. I WORK @* small team, < 15 engineers* many have java bg, but not all, most w/ little to no scala experience* most have oop bg, varying knowledge of FP topics
  9. 9. WE USE SCALA { a lot }* 15+ public facing services supported by many other internal modules/libs* most built on netty, also I/O bound* originally java, now > 70% scala
  10. 10. libraryDependencies += “org.scalaz” %% “scalaz-core” % “6.0.3”* almost all our services depend on scalaz* usage levels and parts of scalaz used vary among services* blocked on upgrading to 6.0.4 b/c of binary compatibility issues
  11. 11. SOMEEXAMPLES
  12. 12. JSON Mapping def Fi leMani def re festJS ad(jso ONR =    ma n: JVa new JS nifest lue) = ONR[ Ap NoId.a p I D= > F field( pplyJS ileMan jsonMa O N( ifest] f i e l d( nifest { )(json change K e y) , ) LogEnt  } ryCach edJson} K e y)* lift-json-scalaz (https://github.com/lift/framework/tree/master/core/json-scalaz)* validationnel applicative, error accumulation = better user-facing errors & debugging* composition
  13. 13. S @-@ A / State[S,A] for { mbE   _ xis <- ts   _ man <- <- ife man } y cha stF ife iel nge ile stF d m Log s - ile bEx Ent = p s m ist ryF ath emb s ile er s - pat =? h (pa th, mbE xi sts >| fal se | t rue )* easy manipulation of highly nested case classes (ex: file manifests)* better implementation hiding* rich libraries (e.g. MapLens, SetLens, & provided state actions)
  14. 14. sideEffect.pure[IO] ble ,X] [ Thr owa = { io n NEL in g]) _)) al i dat st [ Str mai n] ( X ]=V : Li mDo y pe V[ s (ke ys [Cu sto  t tch K ey t .fe tch ain ]]) def fe buc ke tom Dom ap ( Cus ke y s.m pti on[   qu e nce ce[ V,O   .se seq uen    (_.   . map      }* can’t guarantee purity, can delineate impurity* examples: storing data in riak, uploading files to s3 and phonegap build svc* composition of IO makes side-effecting code much more reusable
  15. 15. Kle ] i sli ] OptionW[A] Tree[A] F[_ [M [_] le[ ,A, Pure[P[_] B] ] ab MAB[M[ _],A,B] ld Bind[Z[ [A] _ ]] ro Fo Ze t[ A] Tra ty Lis ver Identity ] NonEmp p [ A e [T s u Fun [_]] r o ctor mig Appl [F[_] Se y[A[_ ] MA[ M[_ ],A] ]]* we make use of a lot more as well* data structures like Validation and NonEmptyList* most type classes and “enrichments”
  16. 16. ITS NOT ALL OR NOTHING* shades of grey, not black and white* scalaz is really many libraries, use the parts you want* we started using “encrichments” and some data structures, grew from there--original image: http://www.chicagonow.com/chicago-tough/files/2012/03/chipsallin.jpg
  17. 17. MAKE BORDERS* don’t abuse scala’s flexibility & power* toss pure/impure code into a salad bowl & mixing is a bad idea* define borders where pure code meets impure code--original image: http://media.nowpublic.net/images//59/4/59455eabd625a15e2afb583dcfbb27ce.jpg
  18. 18. Public Interface Implementation Dependency Calls* your code can be pure* public interface is the border, it runs IO, throws exceptions, etc* existing libraries probably aren’t pure -- many are java after all
  19. 19. Outside World Business Logic* communicate with clients via HTTP Data Access* the most important part -- your code -- make pure** perform side-effects like talk to database, read/write files, etc
  20. 20. Impure Pure Impure* “the sandwich” - common pattern in our code--original image: http://fastfood.ocregister.com/files/2010/05/ice-cream-sandwich1.jpg
  21. 21. :)* code has become much more DRY/modular and as a result more unit testable* concurrent code becomes “simpler” to reason about when pure* FP makes reasoning about bugs simpler, narrow down cause faster
  22. 22. :(* scala hardsips: bin. compatability problems, tooling deficiencies, type inference limits* import scalaz._; import Scalaz._ adds a lot of clutter in the current scope* lack of docs/related content (in Scala!)
  23. 23. scalaz7* not currently used in our production systems but one or two of my side projects* much better for teaching (explicit type class instance usage -- w/o syntax ext.)* addresses some of the issues we have like importing “the scalaz world”
  24. 24. “SCALE”?
  25. 25. “Human Scale”* the complexity comments may be FUD, but that does not mean there is not stuff to learn here* how do we help new employees learn scala & scalaz?
  26. 26. HIRE PEOPLE WHO WANT TO LEARN* hiring from all backgrounds instead of hiring a “scala or java developer” is much easier* those people need to be open to exploring and learning new tech/methods
  27. 27. Shared Resources* easy win, shares effort in finding good resources* dropbox full of downloaded papers and books purchased by the company* internal talks available on github
  28. 28. * code review/pull requests LEARN TOGETHER* face to face discussion on a whiteboard* team talks on fridays, any one can attend, anyone can talk, neither mandatory
  29. 29. ON YOUR OWN* RTFC -- in the end it all just code* apply what you know, this is what really makes you learn it* internal talks mostly make you aware of it, give you starting point, application is key
  30. 30. ITS NOT ALL OR NOTHING* focus on understanding a part of the library* break that part down, use it in the repl in a few cases (w/ a few types, examples, etc)* as you learn more about each part and then more parts the bigger picture emerges--original image: http://www.chicagonow.com/chicago-tough/files/2012/03/chipsallin.jpg
  31. 31. Learn You a ??* not necessary* understanding syntax, basics can be useful while learning concepts until scala docs fill out--haskell logo: http://www.haskell.org/wikistatic/haskellwiki_logo.png
  32. 32. ASK #scalaz FOR HELP
  33. 33. BREAK RULES* you may hear things you cannot do, “validation is not a monad”* ignore and explore yourself -- these are the real learning opportunites* understand how to implement validation monad and why no error accum. happens
  34. 34. PAYING UPFRONT* of course this have some upfront cost* so does writing tests and similarly a good balance pays off
  35. 35. L3 L2 L1 A3 Level A2 A1 Up* scalaz covers most advanced features in scala language* great guide for library and code design (to an extent). Scalaz guys have done serious amount of research in this regard
  36. 36. Thanks!talk recap slide
  37. 37. SOME RESOURCES• Atlassian’s Typeclassopedia - http://typeclassopedia.bitbucket.org• Apocalisp Blog - http://apocalisp.wordpress.com/• “Functional Programming in Scala” MEAP - http://manning.com/bjarnason/• Eric Torreborre’s Blog - http://etorreborre.blogspot.com/• StackMob Engineering Blog - http://www.stackmob.com/category/engineering/• Learn You a Scalaz (my WIP, about to undergo major rework) -https://github.com/jrwest/learn-you-a-scalaz• Chris Marshall’s “Practical Scalaz” Talk - http://skillsmatter.com/podcast/scala/practical-scalaz-2518

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