Re: [boost] Report from Mont Tremblant C++ Committee meeting

From: Fernando Cacciola (fernando_cacciola_at_[hidden])
Date: 2005-10-24 12:11:09

Hamish Mackenzie wrote:
> On Wed, 2005-10-19 at 09:16 -0400, David Abrahams wrote:
>>> Do you think the "fill" example would be useful to fill missing
>>> values in vector< OptionalPointee >?
>>
>> Sorry, I don't understand.
>
> Sorry I was in a hurry and didn't describe what I was thinking better.
> Here is the example from the other email.
>
I get your point.
You're looking for general usages of the Nullable concept (I won't call it 
OptionalPointee anymore).
I like that.

> template< typename OptionalPointee, typename Value_Type >
> Optional_Pointee fill( Optional_Pointee x, Value_Type & default_value
> ) {
>  if( x == none )
>  {
>    x = &default_value; // Does this work with optionals?
>  }
>
>  return x;
> }
>
No, that doesn't work with optional<>.
Furthermore, this is a bad example.
In the usage example below, 'x1' would end up with several pointers to the 
'default_value' object, while 'x2' would end up with several distinct copies 
of 'default_value' wrapped inside optional<>.

But I like the idea of looking for usefull usages of the Nullable concept.

-- 
Fernando Cacciola
SciSoft
http://fcacciola.50webs.com/