An extended version of C++23's std::expected<T, E> to handle variadic errors, allowing usage like expected<T, E1, E2, ...>.
- Compatible with C++17
- Supports multiple error types.
- Enhances standard
std::expectedfunctionality.
Clone the repository:
git clone https://github.com/mguludag/expected.gitInclude the include directory in your project.
Here's a simple example of how to use expected with multiple error types:
#include <mgutility/expected.hpp>
mgutility::expected<int, std::string> divide(int a, int b) {
if (b == 0) return mgutility::unexpected{"Division by zero"};
return a / b;
}
int main() {
auto result = divide(4, 2);
if (!result) {
// Handle error
}
// Use result
}- Chain operations that depend on the success of the previous one, and handle specific errors with
or_else - Transform the value inside
expectedif it is present
#include <mgutility/expected.hpp>
#include <iostream>
#include <string>
#include <system_error>
mgutility::expected<int, std::string, std::error_code> divide(int a, int b) {
if (b == 0) return mgutility::unexpected<std::string>("Division by zero");
if (a < 0) return mgutility::unexpected{std::make_error_code(std::errc::invalid_argument)};
return a / b;
}
mgutility::expected<int, std::string, std::error_code> addOne(int x) {
return x + 1;
}
int main() {
auto result = divide(10, 2)
.and_then(addOne)
.transform([](int x) { return x * 2; })
.or_else([](const std::string& err) -> mgutility::expected<int, std::string, std::error_code> {
std::cerr << "String error: " << err << std::endl;
return mgutility::unexpected<std::string>("Handled string error");
})
.or_else([](const std::error_code& err) -> mgutility::expected<int, std::string> {
std::cerr << "Error code: " << err.message() << std::endl;
return mgutility::unexpected(err.message());
});
if (result) {
std::cout << "Result: " << *result << std::endl;
} else {
// use result.error<std::string>() or result.error()
std::cerr << "Error: " << result.error() << std::endl;
}
}
Contributions are welcome! Please open issues or pull requests.
This project is licensed under the MIT License. See the LICENSE file for details.
This README.md provides a complete guide with basic and advanced usage examples, including multiple error types and chained handling using monadic operations.