Nulang Self-Hosting Bootstrap

Status: Stage 5 — closures with environment capture working. Target: A Nulang→Nulang compiler written in Nulang Core (RFC 0002) that targets the .nbc format (RFC 0001).

Architecture

source.nula
  → compiler_core.nula   (lexer + parser + evaluator in Core)
  → source.nbc            (frozen bytecode artifact)
  → VM::run(nbc)

Files

File	Purpose
host.nula	Host shim
compiler_core.nula	Lexer + Pratt parser + evaluator in Nulang Core
self_test.nula	Core conformance target (fib(10) = 55)
spill_bug_repro.nula	Minimal repro for spill temp clobbering bug (fixed)

Running

nulang bootstrap/compiler_core.nula
# Expected: 42, 7, 9, 43, 200, 6, 36, 11, 8, 7

What's implemented

Stage 3 — Arithmetic + let bindings (2026-07-23)

• Lexer: character-at-a-time scanning via perform String.charAt / String.length.
• Parser: single-function Pratt parser with correct precedence and left-associativity.
• Let bindings: let x = 42 in x + 1 → 43. 2-slot environment (e0, e1).

Stage 5 — Closures with environment capture (2026-07-24)

• Lambdas: fn(x) => x + 1 — parsed inline in the Pratt prefix handler.
• Function application: f(arg) — handled as a postfix operator with highest precedence.
• Environment capture: let a = 3 in (fn(x) => a + x)(5) → 8. The closure captures the defining environment (up to 1 binding, stored in bits 8-15 of the 30-bit closure tag).
• Currying: let add = fn(a) => fn(b) => a + b in add(3)(4) → 7.
• Closure encoding: 30-bit flag 1 << 30 in the high word of the 32-bit value; low 16 bits are the source position. Packed fields: flag | (ph << 23) | (body_start << 16) | (cap_hash << 8) | cap_value.
• Out-of-band sentinel: left == 1 << 40 replaces left == 0 to distinguish "no left operand" from the valid expression result 0.

Register spilling (2026-07-24)

• Inline spilling (commit 06b03c6): no capacity limit.
• Round-robin temp registers (commit db22c67): prevents clobbering in multi-operand spilled reads.

What remains

• HM type inference
• MIR lowering → .nbc codec
• Self-compilation (compiler_core.nula → compiler_core.nbc)
• Multi-binding environment capture (currently limited to 1 captured binding)