(define filter-numbers
  {string --> (list number)}
   File -> (chomp (/. S (input+ number S)) (open File in)))
   
(define chomp
  {((stream in) --> A) --> (stream in) --> (list A)}
   Reader Stream -> (trap-error [(Reader Stream) | (chomp Reader Stream)]
                       		  (/. E (if (eos? (error-to-string E)) 
                                 		(close Stream)
                                 		(chomp Reader Stream)))))
                                 
(define eos?
  {string --> boolean}
  "error: empty stream" -> true
  _ -> false)