hakorune/docs/guides/core-principles.md

Nyash Core Principles — Minimal Syntax, Zero Runtime, Visual Flow

Status: design-only during the feature‑pause (no implementation changes)

Core (one page summary)

• Minimal syntax: { … } + -> + |args| or _ for flow; guard chains as the canonical first-match form. No new match construct; normalize instead.
• Zero-runtime lowering: always desugar to let/if/call/ret/phi. No new opcodes, no implicit closures.
• Capture policy: capture by reference by default; mutation requires mut on the captured binding. Captures remain within the defining scope.
• ASI/format: treat -> as a low-precedence line-continue. Formatter aligns arrows vertically.

Before/After (normalize view)

• Each example documents Ny → normalized Ny → MIR intent (design-only):
  1. Flow serial: {read} -> { |x| validate(x) } -> { |x| save(x) }
  2. Guard chain: guard c1 -> {A}; guard c2 -> {B}; else -> {C}
  3. If horizontal: if cond -> {A} else -> {B}
  4. Range pattern: guard ch in '0'..'9' -> { ... }
  5. Digit helper: acc = acc*10 + ch.toDigitOrNull() (null-guarded)

nyfmt alignment (visual flow)

{ fetch() }
  -> { validate(_) }
  -> { save(_) }

Domain demos (≤20 lines each)

• ETL pipeline: read -> validate -> normalize -> save
• Text/number parse: guard ch in '0'..'9' -> { acc = acc*10 + ch.toDigitOrNull() }
• Mini state machine: guard-first horizontal description with else fallback

Observability (spec hooks; design-only)

• NYASH_SCOPE_TRACE=1|json: enter/exit + captures (JSONL: sid, caps, ret).
• NYASH_FLOW_TRACE=1: desugared steps like t0=B0(); t1=B1(t0);.

Runtime/API additions (docs-only during the feature‑pause)

• StringBox/Utf8Cursor: toDigitOrNull(base=10), toIntOrNull() — compile to simple comparisons/arithmetic.
• Guard sugar: Range ('0'..'9') and CharClass (Digit, AZ, az, Alnum, Space) — compile to bound checks.

Acceptance & guardrails (feature‑pause)

• “No new grammar beyond sugar” and “no new VM opcodes” as hard rules during the feature‑pause.
• Golden texts (Ny → MIR fragments) to lock compatibility where practical.
• Lint proposals are documentation-only: single-use scope, long -> chains, duplicated side effects.

Related docs

• proposals/scope-reuse.md — local scope reuse blocks (MVP)
• design/flow-blocks.md — arrow flow + anonymous blocks
• reference/language/match-guards.md — guard chains + range/charclass sugar
• reference/language/strings.md — UTF‑8 first; proposed digit helpers