Scala

Scala Skill Architecture

1. Skill Context

Focus: Functional Programming on the JVM, Big Data (Apache Spark), highly concurrent systems (Akka, ZIO). Triggers: scala, sbt, functional programming, type classes, implicits, givens, spark, zio, cats.

2. Core Principles

• Pure Functional Programming: Scala encourages writing pure functions without side effects. State is represented through immutable data structures (like List, Vector, Map).
• Expression-Oriented: Almost everything in Scala is an expression that returns a value (including if/else, try/catch, and match).
• Advanced Type System: Scala has one of the most powerful type systems on the JVM, supporting Higher-Kinded Types (F[_]), Intersection Types, and Union Types (Scala 3).

3. Anti-Patterns

• Using var instead of val: Mutable state (var) should be avoided. Use val and create new copies of case classes with the .copy() method.
• Throwing Exceptions: In pure functional Scala, throwing exceptions breaks referential transparency. Use Try, Either, or Option to encode errors in the return type.
• Overusing null: Scala integrates with Java, so null exists, but a Scala developer should never use it. Always wrap potentially absent values in Option.

4. References

• references/scala-fundamentals.md — Case Classes, Pattern Matching, For-comprehensions.
• references/scala-advanced.md — Type Classes, ZIO, Implicits/Givens.
• references/scala-testing.md — ScalaTest and Property-Based Testing.