Six Levels of Scala

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This document describes 6 levels of scala skills that developers can be ranked on. I’m going to use this emeraldjava-scala-six-steps github project to track various scripts and implementation examples as i attempt to educate myself about scala.

Level A1: Beginning application programmer

  • Java-like statements and expressions: standard operators, method calls, conditionals, loops, try/catch
  • Class, object, def, val, var, import, package
  • Infix notation for method calls
  • Simple closures
  • Collections with map, filter, etc
  • for-expressions

Level A2: Intermediate application programmer

  • Pattern matching
  • Trait composition
  • Recursion, in particular tail recursion
  • XML literals

Level A3: Expert application programmer

  • Folds, i.e. methods such as foldLeft, foldRight
  • Streams and other lazy data structures
  • Actors
  • Combinator parsers

Level L1: Junior library designer

  • Type parameters
  • Traits
  • Lazy vals
  • Control abstraction, currying
  • By-name parameters

Level L2: Senior library designer

  • Variance annotations
  • Existential types (e.g., to interface with Java wildcards)
  • Self type annotations and the cake pattern for dependency injection
  • Structural types (aka static duck typing)
  • Defining map/flatmap/withFilter for new kinds of for-expressions
  • Extractors

Level L3: Expert library designer

  • Early initializers
  • Abstract types
  • Implicit definitions
  • Higher-kinded types

Some useful resources https://twitter.github.io/scala_school Scala Tutorial Android App

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