map items in collection to values returned from given action

---

Parameters

map collection :integer :string :literal :dictionary :object :inline :block :range
    params :null :literal :block
    action :block :bytecode

Attributes

with	:literal	use given index
parallel	:integer	run each item in its own cooperative fiber; integer caps the number of in-flight fibers

Returns

Examples

copy
print map 1..5 [x][
    2*x
]
; 2 4 6 8 10

copy
arr: 1..5
map 'arr 'x -> 2*x
print arr
; 2 4 6 8 10

copy
map 1..6 [x y][
    print ["mapping" x "and" y "->" x+y]
    x+y
]
; mapping 1 and 2 -> 3
; mapping 3 and 4 -> 7
; mapping 5 and 6 -> 11
; => [3 7 11]

copy
map.with:'i ["one" "two" "three" "four"] 'x [
    (even? i)? -> upper x -> x
]
; => ["ONE" "two" "THREE" "four"]

copy
; .parallel, fan out one cooperative fiber per item.
; Bare flag = unbounded; integer = sliding-window cap.
results: map.parallel 1..5 'x [ pause 100 x*2 ]
; 5 fibers run concurrently; ~100ms total instead of ~500ms
; ⚠ each fiber gets a SHALLOW COPY of parent symbols;
; writes don't leak back. Return values; don't mutate
; outer state inside the body.

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