Re: [boost] [optional] rebinding references

From: Yuval Ronen (ronen_yuval_at_[hidden])
Date: 2005-10-25 11:59:27

Fernando Cacciola wrote:
> So my current proposal would be:
> 
> Remove direct-assignment.
> Let copy-assigment be the only way to define the wrapped value
> Add make_optional() and make_optional_ref() as shorcuts to help with 
> copy-assignment
> Keep none-assignment as the only wat to clear the wrapped value.

Does this mean that construction from T is also suggested to be removed? 
I assume not...

Anyway, If I'm required to write

optional<T> o = x;
...
o = optional<T>(y);

or

optional<T> o = x;
...
o = make_optional(y);

then it should be considered that this generates an additional temporary 
instance of y (of type T). Direct assignment from T doesn't suffer from 
this. Working around this makes me write

optional<T>(y).swap(o);

or

make_optional(y).swap(o);

which is completely different...