In C++, can we use { } for C-Style casting?

Question

While I have been reading about datatype conversion, I saw this example:

void intval()
{
    for (char c; cin >> c; )
    cout << "the value of '" << c << "' is " << int{c} << '\n';
}

I know that we can cast using:

1. int(c)
2. (int) c
3. static_cast<int>(c)

My questions:

Q1: Is int{c} another way of casting data types?

Q2: After some research on the net, I know that C++ casting is different and it have the compiler check the casting possibility at the compile time, but what are the differences between 1 and 2? And how int{c} is different if it is just another casting way?

Q3: Are there any other ways to explicitly convert/cast?

Answer 1

Is int{c} another way of casting data types?

Yes. T{value} creates a temporary of type T that is direct-list-initialized with the specified braced-init-list. This cast does have an advantage over T(value) in that T{value} can be used to create a temporary array. That would be done like

int main() {
    using int_array = int[5];
    for( auto e : int_array{1,2,3,4,5})
        std::cout << e;
}

It also comes with the caveat that a narrowing conversion is a error

int main() {
    int(10000000000ll);  // warning only, still compiles
    int{10000000000ll};  // hard error mandated by the standard
}

After some research on the net, I know that C++ casting is different and it have the compiler check the casting possibility at the compile time, but what are the differences between 1 and 2?

The big difference between T(value) and (T)value is that in T(value), T must be a single word. For example

int main() {
    unsigned int(10000000); // error
    (unsigned int)10000000; // compiles
}

Q3: Are there any other ways to explicitly convert/cast?

Well in C++ they want you to use the C++ casts which are static_cast, reinterpret_cast, dynamic_cast, and const_cast. Those are preferred over c style cast as a c style cast will do all of those where the C++ versions have certain limitations and come with certain guarantees.

Answer 2

int(c) is the the C++ version of the C-style cast (int)c. It first attempts a const_cast<int>(c), then (failing that) a static_cast<int>(c) followed by reinterpret_cast.

int{c} is a slightly different kettle of fish. Strictly, this is list initialization and has more stringent rules. In particular, narrowing conversions are not allowed, i.e.

int x;
char s{x};  // error

Therefore, it is recommended to use this (rather than casts) unless you know that narrowing conversions are acceptable.

For other than builtin types, there is, in addition to the casts mentioned above, also dynamic_cast.