Re: [Gpsbabel-code] Fix for partial ordering in duplicate.c

[Ron P. <ro...@pa...>]

At 09:58 AM 6/25/2003 -0500, Robert Lipe wrote:
 >If so, it's odd that we have different comparisons for date and index.
 >	If exported if a < b return 1
 >	if index    if a < b return -1
 >is that right?

Yep, that's right.  The reason is that we want to sort in reverse order
by date, but forward order by index.  So if we have four records:

    date      index
    June 24    0
    June 25    1
    June 25    2
    June 24    3

we want to sort them like this:

    date      index
    June 25    1
    June 25    2
    June 24    0
    June 24    3

Thus, the first point we come across is the latest point, but if we
have two points with the same export date/time, we will first see the
one with the smaller index (i.e. the first of those two points that we
came across while importing waypoints.)

In the (common) case that we have no exported dates, the dates will all
be zero so the sort will end up being an expensive no-op (expensive
because, sadly, quicksort can be O(n^2) on presorted elements.)