Beginner's question

[Pierre Couderc]

What is the difference between these 2 ways of writing :

myClass a;
a=b;

and
myClass a=b;
I wrongly thought they were identical (MSVC6).

Thank you in advance.

Pierre Couderc

 

[Srini]

myClass a;

a=b;

The first staement would perform default iniitalization by calling the
default constructor of myClass. The second statement would call the
assignment operator of myClass.

myClass a=b;

This would perform copy initialization. Copy initialization means the
object is initialized using the copy constructor, after first calling a
user-defined conversion if necessary.

Thank you in advance.

Pierre Couderc

Srini

 

[Alipha]

What is the difference between these 2 ways of writing :

myClass a;
a=b;

a is default constructed first, then the assignment operator is used to
assign b to a.

and
myClass a=b;

This is initialization, not assignment. This is identical to:

myClass a(b); // if b is the same type as a

or:

myClass a(myClass(b)); // if b is of different type

In either case, the copy constructor and possibly another constructor
are called and no assignment operator is used.