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flow: timeout combinator — cooperative step budget + 7 tests (Phase 2 complete)
(timeout budget node) bounds a node deterministically: nodes opt in via (tick),
budget ticks are allowed, the next raises flow-timeout. No scheduler/clock in pure
SX so the budget is a step count, not wall-clock. Budgets nest and are per-run.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-06 16:42:16 +00:00

1.8 KiB

flow-on-sx Scoreboard

All tests pass: 49 / 49 across 2 suites.

bash lib/flow/conformance.sh

Per-suite breakdown

Suite Passing Covers
basic 18 Phase 1: single nodes, linear sequence, data-flow threading, defflow, parallel fan/join, nested composition, publish-shaped flow
control 31 Phase 2: branch (6); error model fail/failed?/fail-reason (6); try-catch (6); retry n (6); timeout cooperative step budget (7)

Architecture

Flow combinators are a Scheme prelude (lib/flow/spec.sx) loaded onto scheme-standard-env. A flow is a Scheme procedure input -> output. The whole flow executes inside the Scheme interpreter, so Phase 3's suspend (call/cc) will capture the flow continuation directly.

  • lib/flow/spec.sx — combinators: flow-node, flow-id, flow-const, sequence, parallel, defflow; flow-load-combinators!.
  • lib/flow/api.sxflow/start (Scheme); flow-make-env, flow-run, flow-run-in (SX helpers).
  • lib/flow/tests/basic.sx — 18 cases.
  • lib/flow/conformance.sh — loads substrate + flow layer, runs suites.

Semantics notes

  • node = 1-arg Scheme procedure; the upstream value is the argument. A node ignoring its argument is effectively a thunk.
  • sequence threads left-to-right; empty sequence = identity.
  • parallel fans the same input to every branch and joins results into a list. Evaluation is sequential for now; true concurrency arrives in Phase 3.

Phases

  • Phase 1 — Declarative DAG + sequential execution (combinators + 18 tests, flow/start)
  • Phase 2 — Control flow + error handling (branch, error model, try-catch, retry, timeout)
  • Phase 3 — Suspend / resume (the showcase)
  • Phase 4 — Distributed nodes via fed-sx