diff --git a/2022/15.cpp b/2022/15.cpp
new file mode 100644
index 0000000..d2595de
--- /dev/null
+++ b/2022/15.cpp
@@ -0,0 +1,181 @@
+#include <array>
+#include <cstdint>
+#include <iostream>
+#include <cmath>
+#include <set>
+#include <sstream>
+#include <vector>
+
+#include <boost/phoenix.hpp>
+#include <boost/range/irange.hpp>
+#include <boost/spirit/include/qi.hpp>
+
+#include <doctest.h>
+
+#include <aocpp/Startup.hpp>
+#include <aocpp/Coord.hpp>
+
+namespace {
+
+namespace phx = boost::phoenix;
+namespace qi = boost::spirit::qi;
+
+struct Entry {
+  aocpp::Coord sensor;
+  aocpp::Coord beacon;
+};
+
+using Input = std::vector<Entry>;
+
+// Input file grammar
+template <typename It>
+class Grammar : public qi::grammar<It, Input()> {
+  qi::rule<It, aocpp::Coord> coord;
+  qi::rule<It, Entry()> entry;
+  qi::rule<It, Input()> input;
+
+public:
+  Grammar() : Grammar::base_type{input} {
+    using namespace qi::labels;
+
+    coord = "x=" >>
+            qi::long_long [ phx::bind(&aocpp::Coord::x, _val) = _1 ] >>
+            ", y=" >>
+            qi::long_long [ phx::bind(&aocpp::Coord::y, _val) = _1 ];
+    entry = "Sensor at " >>
+             coord [ phx::bind(&Entry::sensor, _val) = _1 ] >>
+            ": closest beacon is at " >>
+            coord [ phx::bind(&Entry::beacon, _val) = _1 ] >>
+            "\n";
+    input = *entry;
+  }
+};
+
+/// Parse the complete input stream according to the rules defined in 'Grammar'.
+/// Throws: std::runtime_error on failed parse
+auto Parse(std::istream & in) -> Input
+{
+  auto result = Input{};
+  auto const content = std::string{std::istreambuf_iterator{in}, {}};
+  auto b = content.begin(); // updated on successful parse
+  auto const e = content.end();
+
+  if (!qi::parse(b, e, Grammar<decltype(b)>{}, result) || b != e) {
+    throw std::runtime_error{"Bad input file: " + content};
+  }
+
+  return result;
+}
+
+struct Range {
+  std::int64_t lo, hi;
+  auto operator<=>(Range const& rhs) const = default;
+};
+
+template <std::size_t N>
+auto subtract(
+  std::array<Range, N> x,
+  std::array<Range, N> y,
+  std::vector<std::array<Range, N>> & out
+) -> void
+{
+  for (std::size_t i = 0; i < N; ++i) {
+    if (x[i].lo < y[i].lo) {
+      auto z = x;
+      z[i].hi = std::min(z[i].hi, y[i].lo);
+      out.push_back(z);
+    }
+    if (x[i].hi > y[i].hi) {
+      auto z = x;
+      z[i].lo = std::max(z[i].lo, y[i].hi);
+      out.push_back(z);
+    }
+    x[i].lo = std::max(x[i].lo, y[i].lo);
+    x[i].hi = std::min(x[i].hi, y[i].hi);
+    if (x[i].lo >= x[i].hi) {
+      return;
+    }
+  }
+}
+
+auto Segment(std::int64_t center, std::int64_t radius) -> Range {
+  return { center - radius, center + radius + 1};
+}
+
+auto Square(aocpp::Coord center, std::int64_t radius) -> std::array<Range, 2> {
+  return { Segment(center.x + center.y, radius), Segment(center.x - center.y, radius)};
+}
+
+auto Corner(std::array<Range, 2> const& s) -> aocpp::Coord
+{
+  return { (s[0].lo + s[1].lo) / 2, (s[0].lo - s[1].lo) / 2};
+}
+
+auto Part2(Input const& input) -> void {
+
+  auto region = std::vector<std::array<Range, 2>>{Square({2'000'000, 2'000'000}, 2'000'000)};
+  auto region_next = std::vector<std::array<Range, 2>>{};
+
+  for (auto const& entry : input) {
+    auto radius = aocpp::Norm1(entry.beacon - entry.sensor);
+    auto s = Square(entry.sensor, radius);
+    for (auto const& x : region) {
+      subtract(x, s, region_next);
+    }
+    std::swap(region, region_next);
+    region_next.clear();
+  }
+
+  for (auto const& entry : region) {
+    auto corner = Corner(entry);
+    //if (0 <= corner.x && corner.x <= 4000000 &&
+    //    0 <= corner.y && corner.y <= 4000000)
+    //{
+      std::cout << corner << " " << 4'000'000 * corner.x + corner.y << std::endl;
+    //}
+  }
+}
+
+} // namespace
+
+TEST_SUITE("2022-15 examples") {
+  /*
+  TEST_CASE("1D subtraction") {
+    CHECK(subtract<1>({1,3}, {4,5}) == std::vector<std::array<Range, 1>>{{1,3}});
+    CHECK(subtract<1>({4,5}, {1,3}) == std::vector<std::array<Range, 1>>{{4,5}});
+    CHECK(subtract<1>({1,3}, {2,4}) == std::vector<std::array<Range, 1>>{{1,2}});
+    CHECK(subtract<1>({1,3}, {0,2}) == std::vector<std::array<Range, 1>>{{2,3}});
+    CHECK(subtract<1>({1,3}, {1,3}) == std::vector<std::array<Range, 1>>{});
+    CHECK(subtract<1>({1,4}, {2,3}) == std::vector<std::array<Range, 1>>{{1,2}, {3,4}});
+    CHECK(subtract<1>({1,4}, {2,4}) == std::vector<std::array<Range, 1>>{{1,2}});
+    CHECK(subtract<1>({1,4}, {1,3}) == std::vector<std::array<Range, 1>>{{3,4}});
+  }
+  */
+
+  TEST_CASE("documented example") {
+    auto in = std::istringstream{
+      "Sensor at x=2, y=18: closest beacon is at x=-2, y=15\n"
+      "Sensor at x=9, y=16: closest beacon is at x=10, y=16\n"
+      "Sensor at x=13, y=2: closest beacon is at x=15, y=3\n"
+      "Sensor at x=12, y=14: closest beacon is at x=10, y=16\n"
+      "Sensor at x=10, y=20: closest beacon is at x=10, y=16\n"
+      "Sensor at x=14, y=17: closest beacon is at x=10, y=16\n"
+      "Sensor at x=8, y=7: closest beacon is at x=2, y=10\n"
+      "Sensor at x=2, y=0: closest beacon is at x=2, y=10\n"
+      "Sensor at x=0, y=11: closest beacon is at x=2, y=10\n"
+      "Sensor at x=20, y=14: closest beacon is at x=25, y=17\n"
+      "Sensor at x=17, y=20: closest beacon is at x=21, y=22\n"
+      "Sensor at x=16, y=7: closest beacon is at x=15, y=3\n"
+      "Sensor at x=14, y=3: closest beacon is at x=15, y=3\n"
+      "Sensor at x=20, y=1: closest beacon is at x=15, y=3\n"
+    };
+    auto const input = Parse(in);
+  }
+}
+
+auto Main(std::istream & in, std::ostream & out) -> void
+{
+  auto const input = Parse(in);
+  //out << "Part 1: " << Part1(bottom, world) << std::endl;
+  Part2(input);
+}
diff --git a/2022/CMakeLists.txt b/2022/CMakeLists.txt
index 68c2069..e14c5ab 100644
--- a/2022/CMakeLists.txt
+++ b/2022/CMakeLists.txt
@@ -34,6 +34,9 @@ target_link_libraries(2022_13 aocpp Boost::headers)
 add_executable(2022_14 14.cpp)
 target_link_libraries(2022_14 aocpp Boost::headers)
 
+add_executable(2022_15 15.cpp)
+target_link_libraries(2022_15 aocpp Boost::headers)
+
 add_executable(2022_16 16.cpp)
 target_link_libraries(2022_16 aocpp Boost::headers)
 
diff --git a/lib/include/aocpp/Generator.hpp b/lib/include/aocpp/Generator.hpp
index 3348708..ed530c1 100644
--- a/lib/include/aocpp/Generator.hpp
+++ b/lib/include/aocpp/Generator.hpp
@@ -58,7 +58,7 @@ public:
     ~Generator() { if (h_) h_.destroy(); }
     std::optional<T> operator()()
     {
-      h_();
+      h_.resume();
       if (h_.promise().exception_) {
           std::rethrow_exception(h_.promise().exception_);
       }