Re: [boost] [optional] Reference assignment

From: Joel de Guzman (joel_at_[hidden])
Date: 2003-10-31 00:26:28

Brian McNamara <lorgon_at_[hidden]> wrote:

[...]

> Why doesn't this:
> 
>    template <class T>
>    class match {
>       optional<T> data;
>       ...
>    public:
>       match( T x ) : data(x) {}
>       ...
>       void value( T y ) {
>          *data = y;
>       }
>    };
> 
> do what you want?  If T is a reference type, the match's constructor
> puts the reference in the optional, and then calls to value() change the
> value of the referred-to object.  If T is a non-reference type, it also
> works, as far as I can tell.
> 
> I am clearly missing something, but I don't know what.  :)

Oh yes, you can always coerce an API to have it your way <wink ;>

Give me a practical example that shows why your preferred semantics 
is better than the tried and true semantics of true C++ references.
I've given mine, following the premise that the match<T> is conceptually 
an optional<T>. IMO, the match<T> perfectly fits the description of an 
optional<T>. Hence, a use case.

Regards,
-- 
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net