Overview
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.
Code Example
#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;
}
}Motivation
This implementation was created for use in CPPurses.
Installation
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
Documentation
Doxygen documentation can be found here.
Tests
Optional Library uses the google testing framework.
License
This software is distributed under the MIT License.