#| read historical data for Consumer Price Index 
 from ftp://ftp.bls.gov/pub/special.requests/cpi/cpiai.txt
 Since this changes slowly, I just cache the result in a file.
 This is meant to be read by http://ap5.com/loadurl.lisp
 so I use ap5::wget to read the url.  
 I assume the user won't mind if I save an extra file...
|#

(ap5::wget "ftp://ftp.bls.gov/pub/special.requests/cpi/cpiai.txt"
      "ap5.com:cpiai.txt" "--passive-ftp")

(defun read-cpi (file)
  (with-open-file (f file)
    ;; elementary page scraping
    ;; the data starts after a line containing YEAR
    ;; intentionally get an error if we don't find that line
    (loop until (search " YEAR" (read-line f) :test 'string-equal) do nil)
    ;; the line actually has an index for every month, but I settle
    ;; for just the Jan data
    (loop with line with pair
      while (setf line (read-line f nil nil))
      when (setf pair (ignore-errors ;; in particular, one blank line
			(with-input-from-string
			 (s line)
			 (list (read s) (read s)))))
      collect pair)))

;; Now there's some choice of how to use this data.
;; I'd just as soon NOT read it on every access.
;; The easiest thing is to use an internal ap5 relation.

(defrelation cpi
  :documentation "(cpi year index) - consumer price index data from BLS"
  :arity 2 :representation tree :types (integer number))

(loop for (x y) in (READ-CPI "ap5.com:cpiai.txt")
  do (ap5::++ cpi x y))