Programming Languages
Layer 2 across the board: individual languages hold their shape for 5–10 years, and the concepts under them do not decay at all.
Clusters
Section titled “Clusters”General-purpose
Control flow, error handling, module systems and standard-library shape transfer readily — the second language costs a fraction of the first.…
Systems-level
Manual memory management, ownership, layout and undefined behaviour transfer across all four and back down into every managed runtime’s performance…
JVM family
The JVM itself transfers completely — bytecode, class loading, GC behaviour, tooling. Language semantics diverge sharply: Scala’s type system shares…
Data & scientific
The vectorised/array mental model transfers across all of them and is the actual content. Library ecosystems do not, and are the bulk of the daily…
Mobile-first
Modern-language features — null safety, structured concurrency, value types — transfer. Platform APIs are the real cost and transfer to nothing.
Functional
Immutability, algebraic data types and effect discipline transfer into every other language here, which is the main reason to learn one. Runtime…
Scripting & automation
Pipeline composition, exit-code discipline and quoting rules transfer across shells and decades. PowerShell’s object pipeline is a different model…
Established web
Request-per-process execution and convention-heavy frameworks transfer between the two. Little else does.
Cross-cutting concepts
The Layer-0 core of the whole domain: what makes the next language a diff rather than a subject. Learn it once, in whichever language is at hand.