fast set operations

[Levente Torok]

Dear All,

I was in the need to have a fast set operations such as intersection and complement but the
those that I could use with the current octave versions (<3.0) are very very slow to my needs.
For this reason I wrote a version in STL C++. 
May be not optimal in terms of strorage (I convert everything to STL vector since it has fast iterators)
however this is still 100-500 times faster for vectors with 10^5 elements, at least, 
than the versions currently supplied by octave. I enclose the sources.

l=100000;
x= floor(l * rand(l,1)); y=floor(l * rand(l,1)) ; t=time; z=intersection( x, y ); dt=time -t;
x= floor(l * rand(l,1)); y=floor(l * rand(l,1)) ; t=time; z=intersection2( x, y ); dt2=time -t;
dt / dt2 > 500

Bests,

Levente

(Makefile-s are for personal usage)

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