Because the behavior of copy elision changes from C++17; for this case copy elision is mandatory. Mandatory elision of copy/move operations Under the following circumstances, the compilers are required to omit the copy and move construction of class objects, even if the copy/move constructor and the destructor have observable side-effects. The objects are constructed directly … Read more
First, the cause of this issue: C++ Standard [over.ics.rank]/2.11 defines an order for conversion sequences. It says that a user defined conversion sequence is worse than a standard conversion sequence. What happens in your case is that the string literal undergoes a boolean-conversion (defined at 4.12. This is a standard conversion). It does not use … Read more
When you explicitly implement the interface, you first have to cast the object to the interface, then you can call the method. In other words, the method is only available when the method is invoked on the object as the interface type, not as the concrete type. class Vehicle: IVehicle { public int IVehicle.getWheel() { … Read more
The explicit copy constructor means that the copy constructor will not be called implicitly, which is what happens in the expression: CustomString s = CustomString(“test”); This expression literally means: create a temporary CustomString using the constructor that takes a const char*. Implicitly call the copy constructor of CustomString to copy from that temporary into s. … Read more
Section 10.9.3 of the C# spec spells this out. The short version is that it’s disallowed so that the user can be certain that conversions between reference types and interfaces succeed if and only if the reference type actually implements that interface, and that when that conversion takes place that the same object is actually … Read more
Yes and No. It depends on which version of C++, you’re using. C++98 and C++03 do not support explicit type conversion operators But C++11 does. Example, struct A { //implicit conversion to int operator int() { return 100; } //explicit conversion to std::string explicit operator std::string() { return “explicit”; } }; int main() { A … Read more
The rows you get back from iterrows are copies that are no longer connected to the original data frame, so edits don’t change your dataframe. Thankfully, because each item you get back from iterrows contains the current index, you can use that to access and edit the relevant row of the dataframe: for index, row … Read more
The CF Marshaler isn’t so good at this type of thing and what you’re attempting is unsupported. The problem is that it knows that the first element is unaligned, but it seems to not understand that each element in the array would also be unaligned. You can see the behavior works in this example: [StructLayout(LayoutKind.Explicit, … Read more
The compiler is allowed to make one implicit conversion to resolve the parameters to a function. What this means is that the compiler can use constructors callable with a single parameter to convert from one type to another in order to get the right type for a parameter. Here’s an example class with a constructor … Read more