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Write a structurally recursive function (collect f lon) that takes two arguments, a one-argument function f and a list of numbers lon.

  ::= () | ( . ) 

collect returns a list of items f(i) for every i in lon. For example:

 > (collect square '(1 2 -1 -2 3 -3 5 -4 4)) '(1 4 1 4 9 9 25 16 16)