Scalawags #27: Ask the Scalawags

scalawags-27.md

Scalawags #27: Ask the Scalawags

recorded in the flesh, at the Northeast Scala Symposium 2015, Boston MA USA, in front of a sitting-room-only throng of admirers (and Dustin Whitney)

audio only, no video

your hosts this episode: Josh Suereth, Dick Wall, Seth Tisue

Intro (0:00)

• theme music comes booming out of our state-of-the-art sound system
• will Josh ever replace his ancient laptop?
• Seth hearts the interpreter pattern

Scripting with Scala (4:35)

• Dick liked Josh's talk about writing command line applications using sbt
  • does it work? Seth thought the conscript/sbt interface wasn't maintained
  • of course it works, you can run it: https://github.com/jsuereth/snark
• all three of us like using Scala for small scripting tasks
• improving (or working around) slow JVM startup times:
  • ProGuard
  • Nailgun
  • Zinc
• Paul Phillips' bash automation and meta-automation skills boggle Josh's mind

Rapture, JSON, Dynamic (13:15)

• an audience member liked Jon Pretty's talks about type inference (day 1) and Rapture (day 2)
• Rapture can use the Dynamic trait for accessing fields in JSON objects
  • should we use this power? you lose safety, completion, ...
  • but maybe your JSON is irregular, or its shape isn't known at compile time
• Josh spins tales of battling legacy-API woe with Dynamic

Type inference (22:45)

• Dustin liked Jon's type inference talk
• but is Scala scary?
• Seth: when we're mixing traits together, could there be some way to specify which ones we want to participate in type inference?
  • Dick: "this is not the type you're looking for"
  • example: collections. we usually don't want to see all those Like traits
  • example: Option. we normally want Some(3) to have type Option[Int] but we get Some[Int]
• the compiler could help you more with getting your sealed traits right
  • want to make a Scala programmer wince? say Product with Serializable
  • how about an "algebraic" annotation?

Scalactic and library design (33:00)

• audience: I liked Bill Venners' talk about validation using Scalactic
• library design: work with the standard library, or provide an alternative? Scalaz is its own world
• Josh: hey, if you're going to wrap a Java library or port a Haskell library, take the time to do it the Scala way
• anyone remember iteratees?
• Bill Venners wrote the War and Peace of Scaladoc
• package-level docs are more important than method-level docs
• love for Pamflet
• do the tutorial, then draw the rest of the owl
• docs are for supporting contributors, too

Awesome things (44:00)

• Awesome slides: Marconi Lanna presented his ASCII-art slides in the Scala REPL
  • topic was F-bounded polymorphism
  • here's the code: https://github.com/marconilanna/NEScala2015
• Josh's awesome microphone (which recorded this): see photo below
• Josh denies carrying a straight razor on an airplane
• audience: someone should do an awesome talk about error handling and futures
• Dick likes awesome Task in Scalaz
• Seth cruelly cuts off an awesome discussion on Monadish from Haskell