How would I create a graph, such that the property map (weight of edges) is different in each property map? is it possible to create such a property map?
Like an array of property maps?
I have not seen anyone on the internet using it,could I have an example?
Graph g(10); // graph with 10 nodes
cin>>a>>b>>weight1>>weight2>>weight3>>weight4;
and put each weight in a property map.
You can compose a property map in various ways. The simplest approach would seem something like:
Using C++11 lambdas with function_property_map
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#include <boost/property_map/function_property_map.hpp>
#include <iostream>
struct weights_t {
float weight1, weight2, weight3, weight4;
};
using namespace boost;
int main() {
std::vector<weights_t> weight_data { // index is vertex id
{ 1,2,3,4 },
{ 5,6,7,8 },
{ 9,10,11,12 },
{ 13,14,15,16 },
};
auto wmap1 = make_function_property_map<unsigned, float>([&weight_data](unsigned vertex_id) { return weight_data.at(vertex_id).weight1; });
auto wmap2 = make_function_property_map<unsigned, float>([&weight_data](unsigned vertex_id) { return weight_data.at(vertex_id).weight2; });
auto wmap3 = make_function_property_map<unsigned, float>([&weight_data](unsigned vertex_id) { return weight_data.at(vertex_id).weight3; });
auto wmap4 = make_function_property_map<unsigned, float>([&weight_data](unsigned vertex_id) { return weight_data.at(vertex_id).weight4; });
for (unsigned vertex = 0; vertex < weight_data.size(); ++vertex)
std::cout << wmap1[vertex] << "\t" << wmap2[vertex] << "\t" << wmap3[vertex] << "\t"<< wmap4[vertex] << "\n";
}
Using C++03 with transform_value_property_map
This is mainly much more verbose:
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#include <boost/property_map/transform_value_property_map.hpp>
#include <iostream>
struct weights_t {
float weight1, weight2, weight3, weight4;
weights_t(float w1, float w2, float w3, float w4)
: weight1(w1), weight2(w2), weight3(w3), weight4(w4)
{ }
template <int which> struct access {
typedef float result_type;
float operator()(weights_t const& w) const {
BOOST_STATIC_ASSERT(which >= 1 && which <= 4);
switch (which) {
case 1: return w.weight1;
case 2: return w.weight2;
case 3: return w.weight3;
case 4: return w.weight4;
}
}
};
};
using namespace boost;
int main() {
std::vector<weights_t> weight_data; // index is vertex id
weight_data.push_back(weights_t(1,2,3,4));
weight_data.push_back(weights_t(5,6,7,8));
weight_data.push_back(weights_t(9,10,11,12));
weight_data.push_back(weights_t(13,14,15,16));
boost::transform_value_property_map<weights_t::access<1>, weights_t*, float> wmap1 = make_transform_value_property_map(weights_t::access<1>(), &weight_data[0]);
boost::transform_value_property_map<weights_t::access<2>, weights_t*, float> wmap2 = make_transform_value_property_map(weights_t::access<2>(), &weight_data[0]);
boost::transform_value_property_map<weights_t::access<3>, weights_t*, float> wmap3 = make_transform_value_property_map(weights_t::access<3>(), &weight_data[0]);
boost::transform_value_property_map<weights_t::access<4>, weights_t*, float> wmap4 = make_transform_value_property_map(weights_t::access<4>(), &weight_data[0]);
for (unsigned vertex = 0; vertex < weight_data.size(); ++vertex)
std::cout << wmap1[vertex] << "\t" << wmap2[vertex] << "\t" << wmap3[vertex] << "\t"<< wmap4[vertex] << "\n";
}
Output
Both samples output
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16