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From: Gennadiy Rozental (rogeeff_at_[hidden])
Date: 2002-05-01 12:11:44


Under the slogan: "do not make design decisions" I am inclining to admit
that we do need one more level of indirection. So the step in this direction
would be to introduce policies mixer/builder/adaptor or simply Policies as
just one policy template argument:

template<typename Policies>
class basic_smart_ptr : Policies {

This will accommodate most of other designs. But by default we will use
mi_policies_adaptor, like this:

template<typename StoragePolicy,...>
basic_smart_ptr<mi_policies_adaptor<StoragePolicy,OwnershipPolicy,...> >

where mi_policies_adaptor is defined like this:

template<typename StoragePolicy,...>
struct mi_policies_adaptor : StoragePolicy, OwnershipPolicy

mi_policies_adaptor does not incur any restriction to policies. All our
predefined policy will work with this way. We may also provide
chaining_policies_adaptor (I do not think we need more powerful inheritance
generator facility since we now list of our types ahead of time):
To make our predefined policies work with chaining_policies_adaptor we
could provide chaining_adaptor.

template<template Policy, template Base>
struct chaining_adaptor : Policy, Base

template<typename StoragePolicy,...>
struct chaining_policies_adaptor : chaining_adaptor<StoragePolicy,
chaining_adaptor<OwnershipPolicy, ....> > > >

This wont make hierarchy linear though.

Everybody are free to invent their own adaptors strategy, to handle any
compiler issues. But generic framework we should try to keep simple.



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