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flow: try-catch combinator — reify raised exceptions + 6 tests
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(try-catch node handler) runs node; on a raised exception calls (handler error)
with the reified error via Scheme guard, returns the handler value.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
giles
2026-06-06 16:37:26 +00:00
parent 1731476dc6
commit f3da3b975a
5 changed files with 42 additions and 9 deletions
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4
lib/flow/spec.sx
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@@ -22,6 +22,8 @@
;; (fail reason) — make an explicit failure value (data, not an exception)
;; (failed? x) — is x a failure value?
;; (fail-reason x) — the reason carried by a failure value
;; (try-catch node handler) — run node; if it raises, call (handler error)
;; with the reified error and return the handler's value
(define
flow-combinators-src
@@ -29,7 +31,7 @@
(define
flow-control-src
"(define (branch pred then else)\n (lambda (input) (if (pred input) (then input) (else input))))\n (define (fail reason) (list (quote flow-fail) reason))\n (define (failed? x) (and (pair? x) (eq? (car x) (quote flow-fail))))\n (define (fail-reason x) (car (cdr x)))")
"(define (branch pred then else)\n (lambda (input) (if (pred input) (then input) (else input))))\n (define (fail reason) (list (quote flow-fail) reason))\n (define (failed? x) (and (pair? x) (eq? (car x) (quote flow-fail))))\n (define (fail-reason x) (car (cdr x)))\n (define (try-catch node handler)\n (lambda (input) (guard (e (#t (handler e))) (node input))))")
(define
flow-load-combinators!