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because the argument to f must be a variable integer, but i is a constant integer. This matching is a form of program correctness, and is known as const-correctness.This allows a form of programming by contract, where functions specify as part of their type signature whether they modify their arguments or not, and whether their return value is modifiable or not.
The first two of these, const and volatile, are also present in C++, and are the only type qualifiers in C++. Thus in C++ the term " cv -qualified type" (for c onst and v olatile) is often used for "qualified type", while the terms " c -qualified type" and " v -qualified type" are used when only one of the qualifiers is relevant.
In C and C++, constructs such as pointer type conversion and union — C++ adds reference type conversion and reinterpret_cast to this list — are provided in order to permit many kinds of type punning, although some kinds are not actually supported by the standard language.
Even functions can be const in C++. The meaning here is that only a const function may be called for an object instantiated as const; a const function doesn't change any non-mutable data. C# has both a const and a readonly qualifier; its const is only for compile-time constants, while readonly can be used in constructors and other runtime ...
The word cast, on the other hand, refers to explicitly changing the interpretation of the bit pattern representing a value from one type to another. For example, 32 contiguous bits may be treated as an array of 32 Booleans, a 4-byte string, an unsigned 32-bit integer or an IEEE single precision floating point value.
It returns a reference to std::type_info object, which exists until the end of the program. [8] The use of typeid , in a non-polymorphic context, is often preferred over dynamic_cast< class_type > in situations where just the class information is needed, because typeid is always a constant-time procedure, whereas dynamic_cast may need to ...
When the program calls the speak function on a Cat reference (which can refer to an instance of Cat, or an instance of HouseCat or Lion), the code must be able to determine which implementation of the function the call should be dispatched to. This depends on the actual class of the object, not the class of the reference to it (Cat).
Since function Factorial is marked consteval, it is guaranteed to invoke at compile-time without being forced in another manifestly constant-evaluated context. Hence, the usage of immediate functions offers wide uses in metaprogramming, and compile-time checking (used in C++20 text formatting library).