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; This is the date function
; for reasons of computational simplicity, the date is represented
; as an integer which represents days since jan 1 1900.
; because CLIPS does not capture the return of system calls, the intermediate
; value is stored in a file.
(deffunction get-now ()
(system "date '+%y%t%j' > datefile.dat")
(open "datefile.dat" datefile "r")
(bind ?year (read datefile))
(bind ?day (read datefile))
(close datefile)
( +(div ?year 4) (* ?year 365) ?day)
)
(deffunction elapsed-time (?date)
(- (get-now) ?date))
; is date more than 6 mo ago?
(deffunction six-months (?date)
(< 180 (elapsed-time ?date)))
; is date more than 5 years ago?
(deffunction five-years (?date)
(< 1826 (elapsed-time ?date)))
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