Geometry Boost List: [ggl] rtree query interface

Subject: [ggl] rtree query interface
From: Adam Wulkiewicz (adam.wulkiewicz)
Date: 2011-08-22 22:20:36

Barend Gehrels wrote:
> Hi Adam,
>
>>
>> I now realize that this may be confusing since everybody thinks that
>> predicates works exactly like filters from Boost.Range but they
>> shouldn't. They should work more like Expressions.
>
> Yes, actually I did as well. What is exactly the difference?

Well it isn't commutative and transparent like filters which just 
operates on iterators. index::filter (or a sequence of index:: 
predicates) must be passed just after the tree object and it doesn't 
operate on iterators but calls some searching routine, stores elements 
inside some container (e.g. std::deque) and exposes this container as a 
range.

Think of it like if it was std::map. You may call find() method and find 
a value in a fast way. But you may treat it like a range, get some 
iterator, iterate over all elements and filter some of them. This isn't 
effective.

>> (...)
>> Because everybody thinks: "Oh! Boost.Ranges. I know how it works!"
>> maby it's better to use something else to distinguish between Geometry
>> query and ranges. Function or operator different than.
>
> Yes, if they are different, I agree.

It is a matter of choice. How the user should pass the expression or 
sequence of predicates or wathever to the spatial index?

There are some examples in the previous email.

Regards,
Adam