Boris Mansencal wrote:
Hi,
A newbie question regarding functional/hash.
I would like to use TR1 unordered_map for a 2D point custom data type. For this, I use hash_value from Boost. But I would like to give/pass a context to this function : here, width & height of domain in which are my 2D points. Currently, I declare theses width and height static. My code (in my cpp file) looks like :
static int P_width; static int P_height; std::size_t hash_value(point const& p) { return ((size_t)p.x()<<1)*P_width + (size_t)(p.y()<<1); }
But this solution is not satisfactory as I can not have several instances of my class including the unordered_map, i.e., several domains of different width & height.
Is there a straightforward solution that I have overlooked ?
Is the context-free solution std::size_t hash_value(point const& p) { std::size_t seed( 0 ); hash_combine( seed, p.x() ); hash_combine( seed, p.y() ); return seed; } not working for you? http://boost.org/doc/html/hash/combine.html