Can anyone help me to know more about Data Types?

Question

https://code.sololearn.com/czaGTBED3kCn/?ref=app
👆👆👆 This code returns summation of a long and int.. what will be the data type of the summation?? long??
And there is a multi-line comment.. I have attached the link of the writer.. Since he is not active for a long time I am asking you.. Can you explain that comment?. I mean 32 bits?? In Java I learned long takes 8 bits.. may be.. I am sorry I forgot.. 8 or 16 bits.. But 32 bits?Above, Does the variable a take 32 bits?? And what about others.. I mean String, float, double, char in C++??
And yeah, How to check data type of a variable??

Answer 1

Yes, the result will be a long value, which can be confirmed by including <type_traits> and printing

cout << is_same_v< common_type_t< int, long >, long >;

The gist is that the result should be at least as wide as the wider operand, but for more detailed information, have a look at:

https://www.nayuki.io/page/summary-of-c-cpp-integer-rules

https://en.cppreference.com/w/cpp/language/operator_arithmetic

An integer is at least 2 byte or 16 bit wide, as guaranteed by the standard. Remember, the writer talked about bits, while you probably learned that in Java, a long has 8 bytes (1 byte = 8 bits).

The size of a data type may vary between platforms. You can query the size of any type via the sizeof() operator. Typical values are sizeof( float ) = 4, sizeof( double ) = 8. sizeof( char ) is always 1.

You can obtain information about the type of something via typeid(), but this shouldn't be necessary. Since C++ is a strongly typed language, every data type is fixed and known at compile time.

Answer 2

Do you mean this?

cout << is_same_v< common_type_t< int, long >, long >;

It's a short code snippet to verify the result is indeed a long. To be simple, std::common_type<> determines the type all its arguments can be implicitely converted to, and std::is_same<> yields true if both arguments are the same type, false otherwise. This is basic template metaprogramming, but likely to be over your head for now. I just included it to show a means of verification.

To be able to use typeid(), you need to include the <typeinfo> header. Reference along with an example can be found here:

typeid:
https://en.cppreference.com/w/cpp/language/typeid

<typeinfo>:
https://en.cppreference.com/w/cpp/header/typeinfo

Answer 3

Shadow What did you say in second paragraph.. I mean in 4th and 5th line?

Answer 4

Shadow typeid() isn't working :/

Answer 5

Shadow Yeah.. Ok then I should try this after learning more about cpp.. Thanks