[geos-devel] DouglasPeuckerLineSimplifier port

[strk at refractions.net]

Since I'm porting the new geos::simplify package
it might be worth discussing it a little bit making
it a case study for further refactoring.

The DouglasPeuckerLineSimplifier class takes a 
list of Coordinates and returns a 'simplified'
form of it, using the well known DP algorithm.

The resulting point set is a subset of the input
point set: no new points are added.

In Java (JTS), both input and output are of type 
Coordinate[], with the return being a newly allocated
list of newly allocated Coordinates.

My first attempt at modelling this in C++ has been
using std::vector<Coordinate> for both input and 
output, with return wrapped in an std::auto_ptr 
to model ownership transfer from the allocating
class to the caller, and input being defined
as 'const', to forbid modification of input.

I committed it, so if anyone wants to take
a look at possibly different implementation
before proceeding that'd be appreciated.

Note1: a possible improvement that comes
into my mind at first is using Coordinate
pointers rather then values, and maybe
organized in a list rather then in a vector
modifying input instead of allocating
a new container and new values for output.

Note2: every Geometry type has a
CoordinateSequence as it's lowest level
component. Current default implementation
for that interface is CoordinateArraySequence,
which is a vector of Coordinate values.
The CoordinateSequence interface provides a
toVector() function that returns that vector
of Coordinates values as a const pointer.
Wheter converting this "abstract" type
to a more 'simplify-friendly' one is worth
the conversion cost is not easy to tell
as the CoordinateSequence implementation
is opaque.

Note3: the new class might as well directly
work on CoordinateSequence. Will incurr
in virtual calls penalty, but won't suffer
from the 'conversion' problem in note2.

That's all for now, I'll be debugging other
parts of the code.

--strk; 

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