Re: [boost] compressed_pair initialization

From: Matt Calabrese (rivorus_at_[hidden])
Date: 2006-05-18 17:55:51

On 5/18/06, Howard Hinnant <hinnant_at_[hidden]> wrote:
Actually you don't even need a new type compressed_tuple.  You could
put this functionality straight into tuple.  It'd be a royal pain to
do for tuple sizes greater than 3 or 4 though.  Dave, how many empty
members do you find yourself glomming together?  I often have several
potentially empty members but usually have at least that many non-
empty members to spread them around on (I have one example where
wanted to glom two empty members onto a non-empty member).

True, though one [potential] problem with that would be that compressed
pairs and tuples are allowed to share storage for empty types, whereas a
regular tuple, as far as I know, currently allows users to assume a separate
storage location for each element. This could pose a problem in the rare yet
valid case that programmers compare pointers to the instances or if they use
the address of the object as a unique identifier for the instance. Then
again, I doubt that would impact much, if any users' code, so tuple could be
adapted without much problem. Either way, I definately agree that some form
of tuple with optimized storage would be a great addition to boost.

-- 
-Matt Calabrese