Re: Questions about chapter 11 (Operator Overloading) of TC++PL.
Wayne Shu wrote:
Hi everyone, I am reading B.S. 's TC++PL (special edition).
When I read chapter 11 Operator Overloading, I have two questions.
1. In subsection 11.2.2 paragraph 1, B.S. wrote "In particular,
operator =, operator[], operator(), and operator-> must be nonstatic
member function; this ensures that their first operands will be
lvalues". I know that these operators must be nonstatic member
functions, but why this ensure their first operands will be lvalues?
e.g.
class foo
{
int i;
public:
foo & operator = (int ii) { i = ii; return *this; }
};
foo bar() { return foo(); }
bar() = 10;
here bar() is a rvalue.
I'm surprised - I would expect an error in bar() = 10, and there is not.
Additionally, writing
foo & b = (bar() = 10);
it's possible to obtain an lvalue. However, the rvalue obviously can't
be implicitly casted to an lvalue. I'm quizzed.
2. also in subsection 11.2.2, paragraph 3, "Because of historical
accident, the operators = (assignment), & (addressof), and ,
(sequencing) have predefined meanings when applied to class objects.",
I want to know the mentioned predefined meanings of the these
oprators.
I guess that the operator& returns the address of the object, and the
operator= performs a shallow-copy of the object itself.
Regards,
Zeppe
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