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Scala The good, the bad and the very ugly

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Vanity slide Senior software engineer @ TomTom Using scala for more than a year Stackoverflow (couldn’t miss that) http://techblog.bozho.net @bozhobg (Yes, I’m making presentations about programming languages in PowerPoint with screenshots of code)

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The good functional and object-oriented JVM-based val, type inference expressive DSL-friendly

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The good case classes - immutable, value classes embrace immutability - immutable collections by default automatic conversion from and to Java collections

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The good no null - Option[Foo] Reusing java instruments (e.g. guava, slf4j, even spring and hibernate) goodies – e.g. instantiating collections without unnecessary brackets or type declarations

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Partially applied functions

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Traits Multiple inheritance done right

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The bad tools The compiler is too slow IDE-s (Eclipse and IntelliJ) break sbt (build tool) is buggy ecosystem Many java libraries cannot/should not be used Most frameworks and libraries and in early phase binary incompatible => one artifact for each scala version lambdas are slower than in Java 8

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The bad Heavy in terms of concepts and keywords: implicits, for comprehensions, lazy, case class, case object, currying, partially applied functions vs partial functions => Steep learning curve Syntactic diabetes

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Syntactic diabetes

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Implicits implicit val, implicit def, implicitly, (implicit argument) If anywhere in the execution context there is an implicit definition, any function can read it with(implicit foo: String) => the horror! Saves initialization (e.g. of some tool)

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The bad One thing can be written in many ways and there is no “right” way.

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The bad “Concise” doesn’t necessarily mean fast to write or easy to read

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The bad Productivity – do we gain or lose?

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The very ugly cryptic

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scala> List(1,2,3).toSet()

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res0: Boolean = false List(1,2,3).toSet res0: s.c.immutable.Set[Int] = Set(1, 2, 3)

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Philosophy Should the language stop us from shooting ourselves in the foot? Should this be at the expense of its expressiveness? Where is the balance? Who is scala suitable for?

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Optimistic IDEs are getting better Frameworks are getting mature Twitter and the language author are releasing guidelines and best practices (scala – the good parts) invokeDynamic (SI-8359)

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Conclusion I wouldn’t recommend scala for a general-purpose new project In an actual project most of the defficiencies are relatively easy to overcome I would recommend scala for a small, side module It’s interesting to work with, due to the functional aspect Don’t give the users of your language, API or product all of the possible options – they will misuse them.

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Questions? def ? = ???