namespace GolangLean.Core

/-! # Tiny Go Core (TGC) — abstract syntax.

A small calculus that captures the *essential computation* of Go's
sequential fragment: variables, functions, mutable references (Go's `&`/`*`),
sequencing, and conditionals. Everything in surface Go is intended to
desugar into this kernel.

What is *not* here: types (introduced in a later module), goroutines,
channels, structs, slices, methods, interfaces. The point of starting tiny
is that every theorem we prove about TGC carries over once those
extensions are added compositionally. -/

inductive BinOp where
  | add | sub | mul
  | eq  | lt
  deriving Repr, BEq, DecidableEq, Inhabited

inductive Term where
  | unitT   : Term
  | intLit  : Int  → Term
  | boolLit : Bool → Term
  | var     : String → Term
  | lam     : String → Term → Term            -- λ x. e
  | app     : Term → Term → Term
  | letIn   : String → Term → Term → Term     -- let x = e₁ in e₂
  | ifte    : Term → Term → Term → Term
  | binop   : BinOp → Term → Term → Term
  | refMk   : Term → Term                      -- &e   (allocate)
  | deref   : Term → Term                      -- *e   (read)
  | assign  : Term → Term → Term               -- *p = e
  | seq     : Term → Term → Term
  deriving Repr, Inhabited

end GolangLean.Core