Optional
std::optional can specify if a value is valid or not. It has:
.has_value()to examine if it has value.value()to retrieve the value
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#include <optional>
#include <iostream>
#include <vector>
using namespace std;
void test_optional(){
auto get_ll = [](bool does_return)-> std::optional<size_t> {
if(does_return)
return 1;
else
return {};
};
cout<<get_ll(true).value()<<endl;
if (get_ll(false).has_value()){
cout<<"yay"<<endl;
}
}
int main(){
test_optional();
}
