"Alf P. Steinbach" <alfps@start.no> wrote in message
news:424adf02.811159546@news.individual.net...[color=blue]
> * REH:[color=green]
> > Can some tell me why the chooses the constructor in class B over[/color][/color]
operator B[color=blue][color=green]
> > in class A? Is this not ambiguous?
> >
> > Thanks.
> >
> >
> > #include <iostream>
> >
> > using namespace std;
> >
> > struct A;
> >
> > struct B {
> > B() {}
> > B(const A&) {} // this is choosen
> > };
> >
> > struct A {
> > A() {}
> > operator B() const {return B();} // this is not
> > };
> >
> > int main()
> > {
> > A a;
> > B b;
> >
> > b = a; // ambiguous?
> > }[/color]
>
> Comeau online compilation:
>
> Comeau C/C++ 4.3.3 (Aug 6 2003 15:13:37) for ONLINE_EVALUATION_BETA1
> Copyright 1988-2003 Comeau Computing. All rights reserved.
> MODE:strict errors C++
>
> "ComeauTest.c", line 18: error: more than one user-defined conversion from[/color]
"A"[color=blue]
> to
> "const B" applies:
> function "A::operator B() const"
> function "B::B(const A &)"
> b = a; // ambiguous?
> ^
>
> 1 error detected in the compilation of "ComeauTest.c".
>
> In strict mode, with -tused, Compile failed
>[/color]
That's interesting. Even compiling with all warnings, GCC failed to
complain. I would file a bug report, but I'm not sure which is correct. I
just trying it with VC 2003 ToolKit, and says:
error C2679: binary '=' : no operator found which takes a right-hand operand
of type 'A' (or there is no acceptable conversion)
Which I think is wrong, or at least misleading. I guess I will have to look
in the standard, which is hard for me to comprehend.
