[boost] Re: Re: boost::optional feature request.

From: Edward Diener (eddielee_at_[hidden])
Date: 2003-03-25 12:39:45

David Abrahams wrote:
> Douglas Paul Gregor <gregod_at_[hidden]> writes:
>
>> On Mon, 24 Mar 2003, Edward Diener wrote:
>>
>>> Do you really want the key to an associative container to be an
>>> optional value ? I would be hard-pressed to find a use for that.
>>
>> FWIW, the Signals library actually does this internally (although
>> with boost::any objects instead of boost::optional objects).
>> However, I would contend that the need is too specialized to warrant
>> adding an operator<.
>
> Seems entirely reasonable to me to add it.  It looks like at least two
> people have needed exactly those semantics.  What's the cost?

I am not trying to shoot down the request but could someone give me a
practical example of the case where an optional value which does not exist
( I hope that's the right term for when an optional value has no valid
value ) serves as a key in an associative container ?