Re: [boost] [optional] Reference assignment

From: Joel de Guzman (joel_at_[hidden])
Date: 2003-11-02 21:40:13

Brian McNamara <lorgon_at_[hidden]> wrote:
> On Fri, Oct 31, 2003 at 01:26:28PM +0800, Joel de Guzman wrote:

> Hurray for the current semantics of optional!
>
> I know that sounds sarcastic, but seriously: is there anything wrong
> with this use-case?  As far as I can tell, optional already works fine
> for your needs.  (If it ain't broke, ...)

Hi Brian,

Reading my past few posts, I guess I deserved the sarcasm.
Pardon me for the delay in replying. I just came back from a nice short
weekend vacation. Well, I feel fresh with new prespectives now!... :) 

Well I promised myself to be more objective. Sometimes I lose sight
of different possible perspectives. No, there's nothing seriously wrong with 
your use-case. Yes, optional already works fine for my needs. There are
a few rough edges, however, that seemed to make me feel uncomfortable
and these are all due to the mixed value-pointer-like container-like API. 
I guess I can never be comfortable with it. For example:

    optional<int> o(i);
    o = i2; // A
    *o = i2; // B <same as A>

and for references:

    optional<int&> o(r);
    o = r2; // C
    *o = r2; // D <not same as C>
    
It seems that your preferred semantics (the current semantics) creates
a special case (A is equivalent to B but C is not equivalent to D). Well,
I reckon that I can get by by avoiding optional assignments from T
and just use get() (which I prefer over the, ahemmm, funky *o interface):

    optional<int> o(i);
    o.get() = i2; 

and for references:

    optional<int&> o(r);
    o.get() = r2; 

Perhaps assignments from T is not good? I don't know. I do not have
a strong opinion any more. I can live with whatever is provided. I leave
it up to Fernando to do what he thinks is right. Let me just conclude with
a reminder (from the Zen of Python): 

    There should be one-- and preferably only one --obvious way to do it.

Right now, optional has three:

    o = v;
    *o = v;
    o.get() = v;

Regards,

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