--- "E. Gladyshev" <[EMAIL PROTECTED]> wrote:
>
> --- Peter Dimov <[EMAIL PROTECTED]> wrote:
> > E. Gladyshev wrote:
> > > --- Peter Dimov <[EMAIL PROTECTED]> wrote:
> > >
> > >> unless there are very solid reasons for the allocator parameter. ;-)
> > >
> > > I agree, but the problme is that I don't know whether I have a solid
> > reason or not.
> > > I have to ship my class to someone else. She might have a solid reason, I
> > don't know.
> > > If I supply an allocator parameter, then I am covered and I can sleep
> > well. :)
> >
> > Well... if you ask me, it is better to not offer the functionality until
> > someone explicitly asks for it and gives a reasonable scenario as an
> > example. Features are easy to add, hard to remove, and there is always the
> > possibility that you "pre-included" the wrong feature.
>
> Peter, using your example I put together an allocator class that can be used in
> shared_ptr and
> STL
> at the same time. It is not too pretty but it works. If we could only customize
> the counter
> allocations, that would be it.
>
> namespace boostx
> {
> template< typename A >
> class allocator : public A
> {
> public:
> typedef A::value_type type;
> allocator() {}
>
> type* create()
> {
> type* p = allocate(1, 0);
> try
> {
> p = new(p) type;
> }
> catch(...)
> {
> deallocate( p, 1 );
> throw;
> }
> return p;
> }
>
> void operator()( type* p )
> {
> try
> {
> p->~T();
> }
> catch(...)
> {
> deallocate(p, 1);
> throw;
> }
> deallocate(p, 1);
> }
> };
> };
>
> template < class T, class A = boostx::allocator< std::allocator<T> > >
> struct X
> {
> boost::shared_ptr<T> _data;
> std::vector<T,A> _list;
>
> X( const A& al = A() ) : _list(al)
> {
> A tmp(al);
> _data = boost::shared_ptr<T>( tmp.create(), tmp );
> }
> };
>
> OR if you don't mind dropping the 'const' from the constructor
>
> template < typename T, class A = boostx::allocator< std::allocator<T> > >
> struct X
> {
> boost::shared_ptr<T> _data;
> std::vector<T,A> _list;
>
> X( A& al = A() ) : _list(al), _data( al.create(), al )
> {
> }
> };
>
>
> Eugene
I forgot to mention, if the 'const' is dropped from the constructor, 'A' must be
stateless.
Eugene
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