boost::icl::interval_map::operator+= : entry doesn't get added if value is zero.

[afluriach]

When inserting an entry into a boost::icl::interval_map<float, int>, the entry is not inserted if the value is 0. I am guessing this is a bug that happens when the value evaluates to a boolean false. note: using VS2017, C++14. Issue is present in 1.59 - 1.69 (including C++17 for 1.69)

#include <iostream>
#include <vector>
#include <boost/icl/interval_map.hpp>

using namespace std;
typedef pair<float, float> float_pair;

boost::icl::interval_map<float, int> makeIntervalMap(const vector<float_pair>& intervals)
{
	boost::icl::interval_map<float, int> result;
	int intervalCount = 0;

	for (float_pair entry : intervals) {
		result += make_pair(
			boost::icl::interval<float>::right_open(entry.first, entry.second),
			intervalCount++
		);
	}

	return result;
}

const vector<float_pair> intervals = {
	make_pair(200.0f,250.0f),
	make_pair(100.0f,199.0f),
	make_pair(0.0f,50.0f),
};

int main()
{
	boost::icl::interval_map<float, int> m = makeIntervalMap(intervals);

	for (auto it = m.begin(); it != m.end(); ++it) {
		cout << it->first.lower() << ", " << it->first.upper() << endl;
	}
}

In the same code, the interval_map has one fewer element than it should, with the interval corresponding to value 0 missing, Changing it to use a ones-based index works as a workaround. And if I remove the post-increment and try to assign every interval the value zero, none of them get added.

[jbelloncastro]

That is not a bug. See https://www.boost.org/doc/libs/1_71_0/libs/icl/doc/html/boost_icl/concepts/map_traits.html

• A identity absorber never stores value pairs (k,0) that carry identity elements.
• A identity enricher stores value pairs (k,0).

Maps created with partial_absorber (default) or total_absorber trait will not store neutral/identity/default values.
If you want your map to include 0 value, then you should create your map with:

boost::icl::interval_map<float, int, partial_enricher> m;