Thread: New to programming - Confusion with a bit of code

I would say it is a typo because they should have explained that difference, it might have been overlooked by a proofreader perhaps and the author had simply written it on auto.

There is a difference in technicality, though whether it results in an actual difference depends on what is Pen.

This default initialises the Pen object that is created:

Code:

new Pen

This value initialises the Pen object that is created:

Code:

new Pen()

The difference between default initialisation and value initialisation is stated as:

Originally Posted by C++11 Clause 8.5 Paragraph 6

To default-initialize an object of type T means:
— if T is a (possibly cv-qualified) class type (Clause 9), the default constructor for T is called (and the initialization is ill-formed if T has no accessible default constructor);
— if T is an array type, each element is default-initialized;
— otherwise, no initialization is performed.
If a program calls for the default initialization of an object of a const-qualified type T, T shall be a class type with a user-provided default constructor.

Originally Posted by C++11 Clause 8.5 Paragraph 7

To value-initialize an object of type T means:
— if T is a (possibly cv-qualified) class type (Clause 9) with a user-provided constructor (12.1), then the default constructor for T is called (and the initialization is ill-formed if T has no accessible default constructor);
— if T is a (possibly cv-qualified) non-union class type without a user-provided constructor, then the object is zero-initialized and, if T's implicitly-declared default constructor is non-trivial, that constructor is called.
— if T is an array type, then each element is value-initialized;
— otherwise, the object is zero-initialized.
An object that is value-initialized is deemed to be constructed and thus subject to provisions of this International Standard applying to "constructed" objects, objects "for which the constructor has completed," etc., even if no constructor is invoked for the object's initialization.

So, if you have defined the default constructor for Pen, then there won't be a difference.