-- par-map: general parallel fan-out (ILO-67)
--
-- par-map fn xs [n] > L (R b t)
--
-- Applies `fn` to each element of `xs` in parallel, up to `n` items at a
-- time. Returns one Result per input element in input order. Per-item errors
-- surface as Err in the result list without short-circuiting.
--
-- `n` defaults to num_cpus when omitted. Override with ILO_PAR_MAP_CONCURRENCY.
--
-- Contrast with map (sequential, no error wrapping) and get-many (HTTP-only,
-- fixed 10-connection cap). par-map is the recommended general concurrency
-- primitive for CPU work, parallel I/O, or mixed pipelines.
-- square: CPU-bound fn used for parallelism demo
square x:n>n
*x x
-- double: used with explicit concurrency arg
double x:n>n
*x 2
-- unwrap-r: extract Ok value, 0 on Err (demo only — real code pattern-matches)
unwrap-r r:_>n
?r{~v:v;^_:0}
-- run-demo: exercise par-map with explicit n and default concurrency
run-demo>_
xs=[1 2 3 4 5 6 7 8];sq-rs=par-map square xs 4;prnt (map unwrap-r sq-rs);dbl-rs=par-map double xs;prnt (map unwrap-r dbl-rs)
-- run: ilo run examples/par-map.ilo run-demo
-- expected output:
-- [1, 4, 9, 16, 25, 36, 49, 64]
-- [2, 4, 6, 8, 10, 12, 14, 16]