C / C++ - Type Casting

Implicit conversion

implicit conversion:

int i = 42;
double d = i; // Implicit conversion from int to double

C++-style Casting

• static_cast performs no runtime checks. use it in cases like converting float to int, char to int, etc. Also used in CRTP.
• dynamic_cast: used for handling polymorphism. Only used used in inheritence when casting from base class to derived class.
• const_cast: can be used to remove or add const to a variable.
• reinterpret_cast: used for reinterpreting bit patterns and is extremely low level, primarily for things like turning a raw data bit stream into actual data or storing data in the low bits of an aligned pointer.

Cast to enum

auto foo_enum = static_cast<Foo>(foo_number);

Prevent implicit conversion

The explicit keyword can be applied to a constructor or a conversion operator, to ensure that it can only be used when the destination type is explicit at the point of use, e.g., with a cast.

Type conversion operators, and constructors that are callable with a single argument, must be marked explicit in the class definition.

C-style Casting

Syntax: (new_type)expression

For example: (int)3.5.

A C-style cast is basically identical to trying out a range of sequences of C++ casts, and taking the first C++ cast that works, without ever considering dynamic_cast. More powerful as it combines all of const_cast, static_cast and reinterpret_cast, but it's also unsafe.