link printf

procedure main()  #: Haversine formula
   printf("BNA to LAX is %d km (%d miles)\n",
      d := gcdistance([36.12, -86.67],[33.94, -118.40]),d*3280/5280)  # with cute km2mi conversion
end

procedure gcdistance(a,b)
	a[2] -:= b[2]
   every (x := a|b)[i := 1 to 2] := dtor(x[i])
	dz := sin(a[1]) - sin(b[1])
	dx := cos(a[2]) * cos(a[1]) - cos(b[1])
	dy := sin(a[2]) * cos(a[1])
	return asin(sqrt(dx * dx + dy * dy + dz * dz) / 2) * 2 * 6371
end