> let f = {|fib = [0, 1]| {out: $fib.0, next: [$fib.1, ($fib.0 + $fib.1)]} }
> generate $f | first 5
╭───┬───╮
│ 0 │ 0 │
│ 1 │ 1 │
│ 2 │ 1 │
│ 3 │ 2 │
│ 4 │ 3 │
╰───┴───╯

❯ let f = {|fib| {out: $fib.0, next: [$fib.1, ($fib.0 + $fib.1)]} }
❯ generate $f
Error:   × The initial value is missing
   ╭─[entry #5:1:1]
 1 │ generate $f
   · ────┬───
   ·     ╰── Missing intial value
   ╰────
  help: Provide <initial> value in generate, or assigning default value to closure parameter