Re: [boost] Re: Array support [was SmartPtr (Loki) - auto_ptr/move c'tor issue]

From: Beman Dawes (bdawes_at_[hidden])
Date: 2003-02-04 10:19:40

At 03:35 AM 2/4/2003, Andrei Alexandrescu wrote:
 >"Beman Dawes" <bdawes_at_[hidden]> wrote in message
 >news:4.3.2.7.2.20030203161312.023801a0_at_mailhost.esva.net...
 >> * Should a PBSP supply policies that are prone to be used unsafely?
 >>
 >> I'd say "no" is an acceptable answer, at least for something like the 
T*
 >> conversion in widely used libraries like the Standard Library and 
Boost.
 >>
 >> * Should a PBSP allow user supplied policies to modify interface, 
perhaps
 >> in ways that may be unsafe or even just unfortunate?
 >>
 >> That's tougher. At some point I lose interest in a PBSP if it prevents 
me
 >> from doing the things I want to do, even if I only want to do them in 
the
 >> privacy of my own code.
 >
 >The original SmartPtr design leaves the onus of choosing the right policy
 >combination to the application designer. To me, that's a design I find
 >reasonable and in keep with the spirit of C++. Safer designs are possible
 >that reject policy combinations that "don't go together" at the price of
 >being more complicated or less efficient or less flexible.

Yes, understood.

One of the advantages of a generative approach is the improved ability to 
reject invalid policy combinations.

In the generative experiments I tried a couple of years ago, there wasn't a 
problem with added complexity or less efficiency, but the result was 
definitely less flexible.

A GenVoca or curiously recurring template pattern hierarchy might be able 
to solve all those problems, but they were at the boundary of my skill 
level, so I never tried them.

--Beman