Core concepts

This section defines the plgg ethos — the handful of ideas every package in the family assumes. It is the single source of truth: the per-package pages link back here instead of re-explaining Option, Result, cast, proc, and match.

The whole library follows a few rules:

• Type-driven — model the domain in types first, so the compiler rejects illegal states before they run.
• Absence is a value — use Option, never null/undefined.
• Errors are values — use Result, never throw; expected failures are tagged data you fold by tag.
• Data-last composition — build behavior by piping values through functions, config-first / data-last.
• Exhaustive handling — fold unions with match; the compiler flags a missing case.

The concepts

1. Tagged data (Box) — the Box<Tag, Content> foundation everything is built on.
2. Option, not null — absence as a first-class value.
3. Result, not throw — errors as tagged data flowing through the happy path.
4. Validation with cast — turn unknown into typed values, accumulating errors.
5. Async with proc — pipelines over promises and results, with precise error types.
6. Exhaustive match — pattern matching that the compiler checks for completeness.
7. Data-last composition — pipe and flow, and the config-first idiom.

Once these are familiar, the API details live on the core package pages: Values & effects and Structures & errors.