BigMan wrote:
> I get this error message
>
> "error C2440: 'argument' : cannot convert from 'Type' to 'Type &'"
>
> compiling the following piece of code with VC++ 7.1 (w/o language
> extensions!):
>
>
>
///////////////////////////////////////////////////////////////////////////
>
> class Type
> {
> public:
> Type ( ) { }
> Type( Type& ) { }
> };
>
>
///////////////////////////////////////////////////////////////////////////////
>
> inline Type operator +
> (
> Type const&
> , Type const&
> )
> {
> Type Result;
> return Result;
> }
>
>
///////////////////////////////////////////////////////////////////////////
>
> inline Type operator -
> (
> Type const&,
> Type const&
> )
> {
> Type Result;
> return Result;
> }
>
>
///////////////////////////////////////////////////////////////////////////////
>
> int main
> (
> int,
> char*
> )
> {
> Type a, b, c;
> a - b; // 1
> a - b + c; // 2
>
> return 0;
> }
>
>
///////////////////////////////////////////////////////////////////////////////
>
> Line 1 compiles fine, but line 2 does not. VC++ 7.1 tries to call the
> copy ctor in order to compile line 2 and fails. I cannot see the
> reason to do so.
>
> Please tell me if this code sould compile accoring to the standard. If
> not, explain why.
No, it should not. A tem****ary is created to return the value from both
operators. To bind a const reference to a tem****ary a copy constructor
has to be available (although it doesn't have to be used). In your case
the copy constructor has the form T(T&), which when used to copy some
tem****ary object would cause a reference to non-const to bind to the
tem****ary, which is not allowed. The fix would be to declare your copy
constructor as
Type(Type const&);
if possible, of course.
V
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