(defvar *earth-radius* (the fixnum 6371))

(defun degree-to-radian (deg)

(declare (type single-float deg)

(optimize (speed 3) (safety 0) (debug 0)))

(the single-float (* deg (/ (coerce pi 'single-float) 180))))

(defun distance (lata lnga latb lngb)

(declare (type single-float lata lnga latb lngb)

(optimize (speed 3) (safety 0) (debug 0)))

(let* ((lata-r (the single-float (degree-to-radian lata)))

(lnga-r (the single-float (degree-to-radian lnga)))

(latb-r (the single-float (degree-to-radian latb)))

(lngb-r (the single-float (degree-to-radian lngb)))

(delta-lat (the single-float (- latb-r lata-r)))

(delta-lng (the single-float (- lngb-r lnga-r))))

(* (the fixnum (* (the fixnum *earth-radius*)

2))

(the single-float

(asin (the single-float

(sqrt (+ (expt (sin (/ delta-lat 2)) 2)

(* (cos lata-r)

(cos latb-r)

(expt (sin (/ delta-lng 2)) 2))))))))))

(defun test ()

(let ((increment 2.5))

(time (loop for lata from -90.0 to 90.0 by increment do

(loop for lnga from -180.0 to 180.0 by increment do

(loop for latb from -90.0 to 90.0 by increment do

(loop for lngb from -180.0 to 180.0 by increment do

(distance lata lnga latb lngb))))))))