Initialization of variables

[Alahrs]

Hey,

is there any difference between these three options? In java I only used the '=' one.

int x = 7;
int y (8);
int z {9};

The book I am reading uses {}, is this just personal preference?

EDIT: As I see now that the {} is the C++11 (standard?), so shall I go with this one?

[MiiNiPaa]

in this case there is no difference.

In other cases there can be differences.

1) int x = 7; only can initialize primitive types and call non-explicit single argument constructors on class types.
2) int y (8); can call any constructor, but cannot be used everywhere.
3) int z {9}; does not allows type conversions:

int z = 9.0; //works
int z {9.0}; //does not work 

Also it works where previous one don't. On the other hand it does not work everywhere too.

Scott Meyers spent 10 pages in Effective Modern C++2014 explaining differences between them.

[Alahrs]

Thanks, in my beginner cases it shouldnt really make a difference then. Would you recommend anything in those cases where it doesn't matter? Is there some sort of standard then?

[MiiNiPaa]

Pick one and adhere to it. There is no standard on that.

Even beginners can run into problems:

std::string foo; //Creates empty string
std::string bar{}; //Same
std::string baz(); //Surprise! It declares function without arguments returning string 

std::vector<int> foo(10, 20); //Creates vector with 10 element each having value of 20
std::vector<int> bar{10, 20}; //Creates vector with two elements: 10 and 20 
std::vector<int> baz({10, 20}); //Same as previous 

EDIT:
Problem with (): If there is any way for something to be parsed as function declaration, it will be.
Problem with {}: if there is any way for something braced to be threated as initialization_list, it would be.

[Alahrs]

Thank you for your time explaining it to me. Really appreciate it!