[geos-devel] Problem with returning Coordinate* from CoordinateList accessor

[chodgson at refractions.net]

Ok, I've been lurking on this list for a while now and I think I'd like to 
contribute a thought.

My understanding is that the reason for the "CoordinateList" class is to 
abstract the underlying data storage. However, the only reason for someone to 
implement a subclass of coordinate list would be to make use of the complex 
algorithms that JTS provides - all of which are going to need actual coordinate 
objects to do their work, no? Perhaps we cannot afford to abstract the the data 
access layer when our algorithms are going to be doing a LOT of data access.

It seems to me like it would be more efficient to copy all of one's points into 
Coordinate objects, once and for all, right at the start (in the CoordinateList 
constructor). Then, we could pass around references/pointers to the Coordinates 
without worrying about someone else owning them.

The only time this would be inefficient, I suppose, is if you were doing a sub-
linear-time operation... do we do many of those? We could always implement a 
subclass of coordinate list, with a different underlying data structure, which 
created the Coordinate objects as they were requested (with gets) and just kept 
a list of pointers to the Coordinates it allocated, so they could be destroyed 
when the List was destroyed. It could even be "smart" and cache the Coordinate 
objects in case they were retrieved again (unlikely to happen much in a sub-
linear-time operation).

Just my two cents.