Interpreter

The Interpreter serves as the primary entry point for evaluating Abstract Syntax Tree (AST) nodes. It evaluates all the Expression nodes (and some Statement) and returns a PrimitiveValue.

PrimitiveValue

The PrimitiveValue is the core data abstraction in Yukigo. It is a comprehensive union type that integrates JavaScript native primitives with custom runtime entities required for multi-paradigma support.

export type PrimitiveValue =
  | number
  | boolean
  | string
  | null
  | void
  | undefined
  | PrimitiveValue[]
  | RuntimeFunction
  | RuntimePredicate
  | LogicResult
  | LazyList
  | RuntimeObject
  | RuntimeClass

In Yukigo, the PrimitiveValue is a first-class citizen. This design ensures that any result produced by the interpreter, whether it is a simple scalar, a functional closure, a logic predicate, or a lazy structure, can be:

1. Passed as an argument to functions or predicates.
2. Returned from any evaluable block.
3. Assigned to identifiers within the EnvBuilder context.

Why does it "evaluate" Statements?

The purpose of evaluating Statement nodes is to provide a way to declare things at runtime. For example, we can declare a Variable node with identifier x and body 2 like this:

> x = 2

The Interpreter processes the Variable (a Statement), registers the symbol x in the context, and returns void.

Then, when evaluating the symbol x

> x
2

The Interpreter retrieves the associated PrimitiveValue from the environment.