From: Phil Endecott (spam_from_boost_dev_at_[hidden])
Date: 2008-01-16 11:31:32
Barend Gehrels wrote:
>> Phil Endecott wrote:
>> My particular interest is in efficient containers
>> for points (and perhaps lines) with iterators over 2D ranges; have you
>> done anything like that?
>>
> There are three kinds of iterators can be used in our library:
> - you can use the standard std::for_each to iterate over the points of
> for example a linestring or a multi_point, or a part of a them (using
> begin() end() or so) because it's all std:: container implementation here
> - besides that the library supports a for_each_point which iterates over
> all points of a linestring, polygon, and all multi geometries
> - furthermore the library supports a for_each_segment which iterates
> over all segments of the relevant geometries
> I don't know if this answers your question?
Say I have N points, randomly distributed. I want to iterate over the
M points within some region (e.g. a rectangle), where M is much smaller
than N. I need to be able to do this in much better than O(N) time,
e.g. O(log N + M) time. Or I have N lines and I want to find the M of
them that cross a rectangular region (harder!). I get the impression
that you don't have this sort of thing.
>> - A feature of GTL is that it can accommodate arbitrary point types by
>> means of suitable adapters.
> I don't know the GTL details. However, in our case the geometries
> doesn't contain any data but x and y. If a user wants more, he can
> derive from our point type to include for example SRID or color or
> anything. Or he can implement his own point type. So I think it
> approaches your "arbitrary structs".
Well not if I have lat and long in my legacy code instead of x and y,
for example. I'm not certain how useful this is, but the GTL
proponents were very enthusiastic about it.
Regards, Phil.