Ken Tilton wrote:

Great, Pillsy, you just broke the OP's function. Let us hope it is
indeed "not used?". The Op was accumulating the fn return value, not the original list element. Ergo:

(loop for e in list when (funcall fn e) collect it)

Gauche Scheme:

(filter-map
(^(n) (and (even? n) (* n n n)))
(iota 22))

===>
(0 8 64 216 512 1000 1728 2744 4096 5832 8000)

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