(index-of s needle from?) returns first index of needle in s, or -1.
Optional start offset. Specced in primitives.sx, implemented in both
hand-written primitives.py and bootstrapper templates, rebootstrapped.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Spec (eval.sx, primitives.sx):
- Named let: (let loop ((i 0)) body) — self-recursive lambda with TCO
- letrec: mutually recursive local bindings with closure patching
- dynamic-wind: entry/exit guards with wind stack for future continuations
- eq?/eqv?/equal?: identity, atom-value, and deep structural equality
Implementation (evaluator.py, async_eval.py, primitives.py):
- Both sync and async evaluators implement all four forms
- 33 new tests covering all forms including TCO at 10k depth
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Bootstrap shift/reset to both Python and JS targets. The implementation
uses exception-based capture with re-evaluation: reset wraps in try/catch
for ShiftSignal, shift raises to the nearest reset, and continuation
invocation pushes a resume value and re-evaluates the body.
- Add Continuation type and _ShiftSignal to shared/sx/types.py
- Add sf_reset/sf_shift to hand-written evaluator.py
- Add async versions to async_eval.py
- Add shift/reset dispatch to eval.sx spec
- Bootstrap to Python: FIXUPS_PY with sf_reset/sf_shift, regenerate sx_ref.py
- Bootstrap to JS: Continuation/ShiftSignal types, sfReset/sfShift in fixups
- Add continuation? primitive to both bootstrappers and primitives.sx
- Allow callables (including Continuation) in hand-written HO map
- 44 unit tests (22 per evaluator) covering: passthrough, abort, invoke,
double invoke, predicate, stored continuation, nested reset, practical patterns
- Update continuations essay to reflect implemented status with examples
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Add boundary.sx declaring all 34 I/O primitives, 32 page helpers, and 9
allowed boundary types. Runtime validation in boundary.py checks every
registration against the spec — undeclared primitives/helpers crash at
startup with SX_BOUNDARY_STRICT=1 (now set in both dev and prod).
Key changes:
- Move 5 I/O-in-disguise primitives (app-url, asset-url, config,
jinja-global, relations-from) from primitives.py to primitives_io.py
- Remove duplicate url-for/route-prefix from primitives.py (already in IO)
- Fix parse-datetime to return ISO string instead of raw datetime
- Add datetime→isoformat conversion in _convert_result at the edge
- Wrap page helper return values with boundary type validation
- Replace all SxExpr(f"...") patterns with sx_call() or _sx_fragment()
- Add assert declaration to primitives.sx
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Meta-circular evaluator: the SX language specifying its own semantics.
A thin bootstrap compiler per target (JS, Python, Rust) reads these
.sx files and emits a native evaluator.
Files:
- eval.sx: Core evaluator — type dispatch, special forms, TCO trampoline,
lambda/component/macro invocation, higher-order forms
- primitives.sx: Declarative specification of ~80 built-in pure functions
- render.sx: Three rendering modes (DOM, HTML string, SX wire format)
- parser.sx: Tokenizer, parser, and serializer specification
Platform-specific concerns (DOM ops, async I/O, HTML emission) are
declared as interfaces that each target implements.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
