The C engine: the evaluator, the primitive surface, and the object, type and heap machinery underneath them. Generated from the sources by Doxygen; the version above the title is the release this reference was built from.

The other half

This documents the engine written in C, which is all this repository holds. The library written in x-lang lives in the x-lang repository and has its own reference, generated from the (doc ...) forms in its sources:

x-lang API Reference — every module, class, method and member
Documentation index — the hand-written guides, the specification, and the syntax rulings

Where to start here

Files — every translation unit and header, each with the symbols it defines. src/x-prim/ is the primitive surface; src/x-eval.c is the evaluator; ext/x-expr/ is the expression layer the engine embeds.
Data Structures — the object, base and type structs the whole system is expressed in.
Topics — grouped surfaces, where a group has been declared.

The primitive surface is also specified as data, independently of this reference, in tools/contract/isa.x: a committed descriptor that a gate checks the C against, so the two cannot drift apart silently.