reference - w3toppers.com

Retrieving the list of references to an object in Python

As you can see, it’s impossible to find them all. >>> sys.getrefcount(1) 791 >>> sys.getrefcount(2) 267 >>> sys.getrefcount(3) 98

Why is a c++ reference considered safer than a pointer?

It’s considered safer because a lot of people have “heard” that it’s safer and then told others, who now have also “heard” that it’s safer. Not a single person who understands references will tell you that they’re any safer than pointers, they have the same flaws and potential to become invalid. e.g. #include <vector> int … Read more

How to pass this by ref in C#?

The ref keyword causes Pass by Reference semantics – that is, if the variable is re-assigned in the called function, it will re-assign the variable in the caller as well. Obviously, this only works if a variable2 (which can be re-assigne to) is directly passed as the argument and will not work if an arbitrary … Read more

What does int.class mean

A primitive becoming an Object For primitives, there are Class objects available as constants named TYPE in the corresponding wrapper classes — i.e. int.class is changed to java.lang.Integer.TYPE . For other types, the compiler creates a private member variable in the class being compiled to hold the Class object, and generates code to initialize that … Read more

Rvalues, lvalues and formal definitions

Some preliminary paragraphs first: [basic] 3 An entity is a value, object, reference, function, enumerator, type, class member, template, template specialization, namespace, parameter pack, or this. [dcl.type.simple] 4 The type denoted by decltype(e) is defined as follows: if e is an unparenthesized id-expression or an unparenthesized class member access ([expr.ref]), decltype(e) is the type of … Read more

Why we need to return reference to istream/ostream while overloading >> and

The reason is a combination of several facts. You want to be able to chain input and output operations as in in >> x >> y; out << z << std::precision(10) << t << std::endl; so you must return something that allows operator<< again. Since you want your operator to work on any istream, i.e. … Read more

prolonging the lifetime of temporaries

I’ll answer your question… the other way around. Why did they allowed Foo const& foo = fooByValue(); to begin with ? It makes life (somewhat) easier, but introduces potential undefined behavior all over the place. Foo const& fooByReference() { return fooByValue(); // error: returning a reference to a temporary } This is obviously wrong, and … Read more

C++ strings: [] vs. *

Let’s look into it (for the following, note char const and const char are the same in C++): String literals and char * “hello” is an array of 6 const characters: char const[6]. As every array, it can convert implicitly to a pointer to its first element: char const * s = “hello”; For compatibility … Read more

Why does std::forward have two overloads?

A good place to start would be Howard Hinnant’s answer and paper on std::forward(). Your implementation handles all the normal use-cases correctly (T& –> T&, T const& –> T const&, and T&& –> T&&). What it fails to handle are common and easy-to-make errors, errors which would be very difficult to debug in your implementation … Read more