Re: Can copy assignment operator be const?
The std says that a user-declared copy assignment operator
X::operator= is a non-static non-template member function of class X
with exactly one parameter of type X, X&, const X&, volatile X& or
const volatile X&. Nothing about the operator being const.
I don't think compiler should generate default copy assignment operator.
I belive you are right. Because you can still change the state of a
object even if it the assignment operator is declared const. That is if
the state of this object is separated into another object and that
object is reached thru a pointer. As in the Pimpl Idiom.
I had to use a 'const X & operator=(const X & x) const' instead of a 'X
& operator=(const X & x) const'. But otherwize it seems to behave as
excpected. Anyone see a problem?
<CODE>
struct XImpl {
XImpl(int i):i_(i) {}
int i_;
};
struct X {
X(int i){
pimpl_ = new XImpl(i);
}
~X(){
delete(pimpl_);
}
const X & operator=(const X & x) const {
pimpl_->i_ = x.pimpl_->i_;
return *this;
}
XImpl *pimpl_;
};
inline void TestX() {
const X x1(1);
const X x2(2);
x1 = x2;
X x3(3);
X x4(4);
x3 = x4;
x3 = x4 = x1 = x2;
(x3 = x4 = x1 = x2).pimpl_->i_ = 0;
}
</CODE>
Regards Patrik
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