🚀 go-pugleaf

Martin Aupperle <100754.2730@CompuServe.COM> writes:

>If I define

>  struct  X {

>    X( int );
>    operator const char* () const;

>    /* other members */
>    };

>  X& operator + ( const X&, const X& );

>I cannot say 

>  X x1( 5 );
>  X x2 = x1+3;  // ambiguous

>Borland BC4.5 says that x1+3 is ambiguous. I know that it can
>1. convert 3 to an X and call operator + ( const X&, constX& )
>2. convert x1 to a const char* and do pointer arithmetics. 

>Is the compiler right? I have in mind that a conversion towards a user defined
>type has precedence over the conversion to a fundamental type. So choice (1)
>should be right and it shoud not be ambiguous. 

The compiler is right. The expression x1+3 is treated as if it were
a function call: operator+(x1,3). There are 2 relevant candidates.

1) operator+(const X&, const X&)
2) operator+(char* const, const int)   (built-in pointer arithmetic)

The first form is a better match for the first argument. The second
for is a better match for the second argument. Therefore the construct
is ambiguous.

If you had an operator+(const X&, const int), it would be a best match
and would be used.
-- 
***** The stories about the first lady are hilarious. *****
David Sachs - Fermilab, HPPC MS369 - P. O. Box 500 - Batavia, IL 60510
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