This part in "Using std::optional as an optional function parameter": "However, because std::optional makes a copy of its argument, this becomes problematic when T is an expensive-to-copy type (like std::string). With normal function parameters, we worked around this by making the paramete...
In a return statement, when the operand is the name of a non-volatile object with automatic storage duration, which isn't a function parameter or a catch clause parameter, and which is of the same class type (ignoring cv-qualification) as the function return type. This variant of copy eli...
If you return an optional from a function, then it’s very convenient to return just std::nullopt or the computed value.std::optional<std::string> TryParse(Input input) { if (input.valid()) return input.asString(); return std::nullopt; } In the above example you can see that I ...
Usuallystd::optionalis used in: To return something from a function As an optional input parameter to a function As an optional class member To perform some lazy loading/two-phase init of some object So probably your code will be one of those three above variations… but of course you migh...
If you want to add a new parameter then just extend the structure. But isn’t std::pair<bool, MyType> not similar to std::optional? std::optional From cppreference - std::optional: The class template std::optional manages an optional contained value, i.e. a value that may or may...
How do you write a function that optionally accepts or returns an object? The traditional solution is to choose one of the potential values as a sentinel to indicate the absence of a value: Copy void maybe_take_an_int(int value = -1); // an argument of -1 means "no value" int may...
The Capsule.hh and Ellipsoid.hh have MassMatrix() functions that take no parameters and return a std::optional while Box.hh, Cylinder.hh and Sphere.hh have MassMatrix() functions that have a bool return type and take gz::math::MassMatrix3d object as a parameter. This PR corrects this ...
The more complex approach is to first test forvalid()and only useget()if there is data. The functionget()works this way internally, as you’ll see. The methodinvalid()is for convenience as inwhile(some_var.invalid()) {...}