Modern C++ (C++20) Idioms & Features¶
This project serves as a showcase of modern C++20 design patterns, safety principles, and idiomatic library design.
1. Key C++20 Features Used¶
1.1 Spaceship Operator (<=>) for Three-Way Comparison¶
Rather than writing boilerplate comparison operators (==, !=, <, <=, >, >=), C++20 introduces the defaulted three-way comparison operator:
struct Point {
double x{0.0};
double y{0.0};
[[nodiscard]] auto operator<=>(const Point &) const = default;
};
struct Edge {
NodeId from{0};
NodeId to{0};
Weight weight{0.0};
[[nodiscard]] auto operator<=>(const Edge &) const = default;
};
1.2 std::optional<T> for Explicit Value Semantics¶
Instead of magic sentinel values (such as -1 or DBL_MAX), optionality is explicitly captured by the type system:
// Returns std::nullopt if the target is unreachable
[[nodiscard]] std::optional<Weight> distance_to(NodeId destination) const;
// Returns std::nullopt if no path exists
[[nodiscard]] std::optional<std::vector<NodeId>> path_to(NodeId destination) const;
// Optional seed for deterministic graph generation
[[nodiscard]] static Graph random_geometric(
std::size_t nodes,
std::size_t connections,
std::optional<std::uint64_t> seed = std::nullopt
);
1.3 [[nodiscard]] Attribute¶
To prevent subtle bugs caused by ignoring query results or computed paths, query methods and factories are annotated with [[nodiscard]]:
[[nodiscard]] DijkstraResult shortest_paths(const Graph &graph, NodeId source);
[[nodiscard]] bool has_edge(NodeId u, NodeId v) const;
[[nodiscard]] std::size_t node_count() const noexcept;
1.4 Structured Bindings & Min-Heap Idioms¶
Decomposing tuple-like objects directly into named local variables simplifies code readability:
using QueueElement = std::pair<Weight, NodeId>;
std::priority_queue<
QueueElement,
std::vector<QueueElement>,
std::greater<QueueElement>>
pq;
while (!pq.empty()) {
auto [d, u] = pq.top(); // Structured binding (d = weight, u = node)
pq.pop();
// ...
}
2. Robust Domain Exception Hierarchy¶
Library code must never terminate the process (exit()). Instead, well-typed exceptions derived from std::runtime_error are thrown and can be handled upstream:
graph TD
RuntimeError["std::runtime_error"] --> Base["dijkstra::DijkstraException"]
Base --> Parse["dijkstra::GraphParseException"]
Base --> Node["dijkstra::InvalidNodeException"]
Base --> Weight["dijkstra::NegativeWeightException"]try {
Graph g;
file >> g;
auto result = shortest_paths(g, 0);
} catch (const dijkstra::InvalidNodeException &e) {
std::cerr << "Invalid node: " << e.what() << "\n";
} catch (const dijkstra::GraphParseException &e) {
std::cerr << "Malformed input: " << e.what() << "\n";
}
3. Namespace Decoupling & Header Hygiene¶
- All library components reside in
namespace dijkstra. - Header files never use
using namespace std;to avoid namespace pollution. - Headers are placed in
include/dijkstra/and exported cleanly via CMake target interface properties: