A header only implementation of the Boost::Optional Library.
The Optional template class provides an interface for any type to allow its objects to optionally contain a value. This is useful for a few reasons:
- Templated type does not need a default constructor.
- It expresses intent, making code more readable than pointers or other
workarounds such as
std::pair<T, bool>. - Expensive to construct objects are not created if not needed.
- No dynamic allocations.
Optional objects can be queried for validity by an explicit conversion to bool.
To access the underlying object, the dereference operator* can be used, or
operator-> provides access to the object’s members.
#include <ctime>
#include <iostream>
#include <optional/optional.hpp>
using opt::Optional;
Optional<std::time_t> get_time_if_even() {
auto t = std::time(nullptr);
if (t % 2 == 0) {
return t;
} else {
return opt::none;
}
}
int main() {
auto time_opt = get_time_if_even();
if (time_opt) {
std::cout << "The time was: " << *time_opt << " s" << std::endl;
} else {
std::cout << "No time given." << std::endl;
}
}This implementation was created for use in CPPurses.
CMakeLists.txt will generate files to install headers and build tests.
# In top level project directory
mkdir build && cd build
cmake .. # generate make files
make tests # build tests(optional)
ctest # run tests(optional)
sudo make install # install header files to system include directory
Doxygen documentation can be found here.
Optional Library uses the google testing framework.
This software is distributed under the MIT License.