Re: [boost] [optional] Reference assignment

From: Joel de Guzman (joel_at_[hidden])
Date: 2003-10-31 04:20:50

Brian McNamara <lorgon_at_[hidden]> wrote:
> On Fri, Oct 31, 2003 at 01:26:28PM +0800, Joel de Guzman wrote:
>> 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 ;>
> 
> So does my code above work for you?  If not, can you show me the problem?
> I'm still confused what the issue is here.

Here's one problem with your solution:

    match<int&> m(i);
    m = 3; // compile error

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