Thank you everyone for criticism and comments, exactly kind of feedback (maybe not its contents) I wanted. Didn't expect junk I write (documentation, too) to be so incomprehensible. Except "key named 'value' causing confusion" (too much, no?), looks like I deserved it.

haukex, thank you for intention to suggest better algorithm or data structure -- I deliberately described it (failed to communicate though) as something abstract, it's really not worth anyone's effort.

P.S. As to benchmarking, you all are right again: loop with simple push to new array, of either element or its expansion, is faster than all of the above