问题
I've created a boost::multi_index_container (containerSet) over a container class and indexed the containerSet by std::string and std::set<int>. Is it possible to get the container, which store a specific int inside their set? Furthermore is it possible to get all container, which store at least one value between int1 and int2 within their set?
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/hashed_index.hpp>
#include <boost/format.hpp>
#include <boost/lambda/core.hpp>
#include <iostream>
using boost::multi_index_container;
using namespace boost::multi_index;
class Container {
public:
std::set<int> set;
std::string name;
Container(std::string name, std::set<int> set);
~Container();
friend std::ostream& operator<<(std::ostream& os,const Container& c) {
os << c.name << ", [ ";
for (int i : c.set) {
os << i << " ";
}
os << "]";
return os;
}
};
Container::Container(std::string name = "noName", std::set<int> set = {}) : name{name} ,set{set} {}
Container::~Container() {}
struct setTag{};
struct nameTag{};
typedef multi_index_container<Container, indexed_by<
ordered_unique<tag<nameTag>, BOOST_MULTI_INDEX_MEMBER(Comp, std::string, name)>,
ordered_unique<tag<setTag>, BOOST_MULTI_INDEX_MEMBER(Comp, std::set<int>, set)>
>> ContainerSet;
//don't see how I could get the compare structs to work, because
//a) can't fullfill the strict weak odering requirements and
//b) because of the setTag ordering, not all set's get called
struct compSetRange {
bool operator()(int x,const std::set<int> &c) const {}
bool operator()(const std::set<int> &c, int x) const {}
};
struct compSetFind {
bool operator()(int x,const std::set<int> &c) const {}
bool operator()(const std::set<int> &c, int x) const {}
};
int main() {
Container c1{"c1", {5, 6, 7, 18, 61, 77}};
Container c2{"c2", {2, 4, 5, 21, 36, 88, 99}};
Container c3{"c3", {2, 3, 9, 10, 65, 75, 91}};
ContainerSet cs;
cs.insert(c1);
cs.insert(c2);
cs.insert(c3);
std::cout << "print by name (ordered)" << std::endl;
for (auto e : cs.get<nameTag>()) {
std::cout << e << std::endl;
}
std::cout << std::endl;
std::cout << "print by set (ordered)" << std::endl;
for (auto e : cs.get<setTag>()) {
std::cout << e << std::endl;
}
std::cout << std::endl;
typedef ContainerSet::index<setTag>::type compBySetIndex;
//find(std::set) works but isn't useful in my case
compBySetIndex::iterator it1 = cs.get<setTag>().find(std::set<int>{2, 4, 5, 21, 36, 88, 99});
//TODO: find all comps with int 5 -> c1 and c2
// compBySetIndex::iterator it1 = cs.get<setTag>().find(200, compSetFind());
if (it1 !=cs.get<setTag>().end()) {
std::cout << *it1 << std::endl;
}
//TODO: find all container with values between 70 and 80 -> c1 and c3
// compBySetIndex::iterator it1_low = cs.get<setTag>().lower_bound(70, compSetRange());
// compBySetIndex::iterator it1_upp = cs.get<setTag>().upper_bound(80, compSetRange());
//.range() also not applicable
return 0;
}
With the sets:c3 = {2, 3, 9, 10, 65, 75, 91}c2 = {2, 4, 5, 21, 36, 88, 99}c1 = {5, 6, 7, 18, 61, 77}
I want to be able to call ...find(5); and get at least c2, maybe even c1 on the next invocation. This might be doable with the right Compare function, but I can't think of a way to make the operator() functions compatible.
Furthermore after ...lower_bounds(70) and ...upper_bounds(80) I should get c3 and c1. Because of the ordering of the std::set's, this requirement seems unachievable with boost.
Am I missing something? Thanks in advance!
I know I could do a linear search over all containers and their sets to achieve my goal, but that would negate the performance advantage of the multi_index_container. If boost is the wrong tool for this job I will have to resort to an individual class containerSet.
回答1:
Andrew diagnosed the issue quite accutely.
To help you along, let me advertise a widely under-used library in Boost: Boost Interval Container.
I hope this demo can shed some light on how useful Boost ICL can be.
Live On Coliru
#include <boost/icl/separate_interval_set.hpp>
#include <boost/icl/interval_map.hpp>
#include <boost/multi_index_container.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index/member.hpp>
#include <iostream>
#include <numeric>
#include <vector>
using Set = std::set<int>;
struct io_wrap { Set const& ref; };
static std::ostream& operator<<(std::ostream& os,const io_wrap& s) { os << "[ "; for (auto i : s.ref) os << i << " "; return os << ']'; }
namespace icl = boost::icl;
namespace bmi = boost::multi_index;
struct Record {
std::string name;
Set set;
Record(std::string name = "noName", Set set = {}) : name{name}, set{set} {}
friend std::ostream& operator<<(std::ostream& os,const Record& c) { return os << c.name << ", " << io_wrap{c.set}; }
};
using Map = icl::interval_map<int, std::set<Record const*> >;
using Interval = Map::interval_type;
using Table = bmi::multi_index_container<
std::reference_wrapper<Record>,
bmi::indexed_by<
bmi::ordered_unique<
bmi::tag<struct byName>,
bmi::member<Record, std::string, &Record::name>
>
>
>;
auto interval_set(Set const& is) { return std::accumulate(is.begin(), is.end(), icl::interval_set<int> { } ); }
auto envelope(Record const& r) { return hull(interval_set(r.set)); }
void insert(Map& into, Set const& is, std::set<Record const*> const& rs = {}) {
for (auto i : interval_set(is))
into += Map::value_type { i, rs };
}
int main() {
////////////////////////////////
// Prepare data
std::vector<Record> backing_storage {
{"c3", {2, 3, 9, 10, 65, 75, 91}},
{"c1", {5, 6, 7, 18, 61, 77}},
{"c2", {2, 4, 5, 21, 36, 88, 99}},
// outliers
{"c4", {0}},
{"c5", {200}},
};
Table const byname(backing_storage.begin(), backing_storage.end());
Map cs;
for (auto& r : backing_storage)
insert(cs, r.set, { &r });
////////////////////////////////
// Usage demos
std::cout << "print by name (ordered)\n";
for (auto const& e : byname) { std::cout << " - " << e << " - envelope: " << envelope(e) << "\n"; }
std::cout << "\n";
auto perform_match = [&cs](auto key) {
Map::codomain_type matches;
Map::codomain_combine combine;
for (auto p : cs & key)
combine(matches, p.second);
std::cout << "matching " << key << ":\n";
for (auto const* r : matches)
std::cout << " - " << *r << "\n";
std::cout << "\n";
};
for (auto key : { Set{2}, {99}, {2,99}, {2,99,5} }) {
perform_match(interval_set(key));
}
perform_match(Interval::right_open(70, 81));
}
Prints:
print by name (ordered)
- c1, [ 5 6 7 18 61 77 ] - envelope: [5,77]
- c2, [ 2 4 5 21 36 88 99 ] - envelope: [2,99]
- c3, [ 2 3 9 10 65 75 91 ] - envelope: [2,91]
- c4, [ 0 ] - envelope: [0,0]
- c5, [ 200 ] - envelope: [200,200]
matching {[2,2]}:
- c3, [ 2 3 9 10 65 75 91 ]
- c2, [ 2 4 5 21 36 88 99 ]
matching {[99,99]}:
- c2, [ 2 4 5 21 36 88 99 ]
matching {[2,2][99,99]}:
- c3, [ 2 3 9 10 65 75 91 ]
- c2, [ 2 4 5 21 36 88 99 ]
matching {[2,2][5,5][99,99]}:
- c3, [ 2 3 9 10 65 75 91 ]
- c1, [ 5 6 7 18 61 77 ]
- c2, [ 2 4 5 21 36 88 99 ]
matching [70,81):
- c3, [ 2 3 9 10 65 75 91 ]
- c1, [ 5 6 7 18 61 77 ]
来源：https://stackoverflow.com/questions/44036817/boostmulti-index-container-operations-on-stdset-inside-container