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rose-ash/lib/flow/tests/combinators.sx
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flow: combinator library — tap, recover, map-flow + 11 tests (Phase 5 complete)
tap: side-effecting pass-through (returns input). recover: fail-VALUE counterpart
of try-catch (run node; on (fail r) run handler on r). map-flow: run a node over
each item of a list, join results sequentially. 116/116 across 7 suites.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-06 17:57:48 +00:00

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;; lib/flow/tests/combinators.sx — Phase 5: combinator library (tap, recover, map-flow).
(define flow-cmb-pass 0)
(define flow-cmb-fail 0)
(define flow-cmb-fails (list))
(define
flow-cmb-test
(fn
(name actual expected)
(if
(= actual expected)
(set! flow-cmb-pass (+ flow-cmb-pass 1))
(begin
(set! flow-cmb-fail (+ flow-cmb-fail 1))
(append! flow-cmb-fails {:name name :expected expected :actual actual})))))
(define flow-m (fn (src) (flow-run src)))
;; ── tap (side-effecting pass-through) ───────────────────────────
(flow-cmb-test
"tap: returns input unchanged"
(flow-m "(flow/start (tap (lambda (x) (* x 999))) 7)")
7)
(flow-cmb-test
"tap: runs the side effect"
(flow-m
"(define seen 0) (flow/start (tap (lambda (x) (set! seen x))) 42) seen")
42)
(flow-cmb-test
"tap: value flows on while the effect observes it"
(flow-m
"(define log 0) (flow/start (sequence (lambda (x) (+ x 1)) (tap (lambda (x) (set! log x))) (lambda (x) (* x 2))) 10) (list log (flow/result 1))")
(list 11 22))
;; ── recover (fail-value counterpart of try-catch) ───────────────
(flow-cmb-test
"recover: passes a non-fail value through"
(flow-m "(flow/start (recover (lambda (x) (* x 2)) (lambda (r) -1)) 5)")
10)
(flow-cmb-test
"recover: handles a fail value via the reason"
(flow-m
"(flow/start (recover (lambda (x) (fail (quote too-small))) (lambda (r) (list (quote recovered) r))) 1)")
(list "recovered" "too-small"))
(flow-cmb-test
"recover: handler can supply a default value"
(flow-m
"(flow/start (sequence (recover (lambda (x) (if (> x 0) x (fail (quote neg))) ) (flow-const 0)) (lambda (x) (* x 10))) -3)")
0)
(flow-cmb-test
"recover: does not catch raised exceptions (those are try-catch's job)"
(flow-m
"(flow/start (try-catch (recover (lambda (x) (raise (quote boom))) (flow-const 0)) (lambda (e) e)) 1)")
"boom")
;; ── map-flow (run a node over a list, join) ─────────────────────
(flow-cmb-test
"map-flow: applies the node to each item"
(flow-m "(flow/start (map-flow (lambda (x) (* x x))) (list 1 2 3 4))")
(list 1 4 9 16))
(flow-cmb-test
"map-flow: empty list joins to empty"
(flow-m "(flow/start (map-flow (lambda (x) (+ x 1))) (list))")
(list))
(flow-cmb-test
"map-flow: each item runs an independent sub-flow"
(flow-m
"(flow/start (map-flow (sequence (lambda (x) (+ x 1)) (lambda (x) (* x 2)))) (list 0 4 9))")
(list 2 10 20))
(flow-cmb-test
"map-flow: composes — fan over a list then reduce the join"
(flow-m
"(flow/start (sequence (map-flow (lambda (x) (* x 10))) (lambda (xs) (apply + xs))) (list 1 2 3))")
60)
(define flow-cmb-tests-run! (fn () {:total (+ flow-cmb-pass flow-cmb-fail) :passed flow-cmb-pass :failed flow-cmb-fail :fails flow-cmb-fails}))