After many years of Java development, discovering Scala’s type system and related features was something of a departure for me. Suffice to say GADT wasn’t my first four letter utterance when learning about pattern matching on types, let alone what, when and how to use variance annotations and generalized type constraints. To kick things off, here’s a ‘small but powerful‘ few lines of buzzword bingo on the type system:
…Scala is a statically, strongly, typed language, with implicit type inference and support for structural and existential types. It also features parameterized types, abstract and phantom types and is capable of implicitly converting between datatypes. These core capabilities are utilized by context and view bounds and complimented by generalized type constraints, to provide powerful compile time contracts. Furthermore, Scala supports declaration site type annotations to facilitate invariant, covariant and contravariant type variance…
In a word, Ouch !
In the remainder of this post, I’ll try to demystify these concepts and sew the seeds of intrigue for further investigation.