[boost] Re: Optional, tie, and iterator_adaptor

[Daniel Frey]

Joel de Guzman wrote:
Although I don't see this as problematic:

    optional<int> x;
     if (x)  
        foo(x);

Or perhaps:

    optional<int> x;
     if (!!x)  
        foo(x);

We already have an implicit conversion to safe_bool and an 
operator ! anyway. Keep it. There's nothing wrong with it:

    operator unspecified-bool-type() const;
    bool operator!() const;
IMHO, there is something terribly wrong here because now optional<T> has 
two interfaces. The interface of optional itself and the interface of T. 
If you think that optional<T> can be used like T (having the 
value-interface), you are immediately fooled by if(x) as it doesn't 
check T's value. A pointer-interface is much cleaner as it gives the 
user a hint that he is using a wrapper and in practice, I always prefer 
to be a little more explicit on these things (even at the cost of an 
occasional * here and there) than to have silent bugs.

Regards, Daniel

--
Daniel Frey
aixigo AG - financial training, research and technology
Schloß-Rahe-Straße 15, 52072 Aachen, Germany
fon: +49 (0)241 936737-42, fax: +49 (0)241 936737-99
eMail: [EMAIL PROTECTED], web: http://www.aixigo.de
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