priority queue question

[vaclavpich@atlas.cz]

Hi all,
I want to know your opinion about my implemetaion of priority queue. I
couldn't use std::priority_q ueue so I've written my. I designed two
kinds of interface but I'm not sure that this is good idea.
Please write me what do you think about this :
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 1) first class is similar to std::priority_q ueue
template<
class _Ty,
class _Predicate = Less<_Ty>, // comparator
class _Container = Array<_Ty // like std::vector

>

class PriorityQueuePo licy
{
_Container m_c;
public:
// common interface like std::priority_q ueue
void push(const _Ty& val);
_Ty& top();
void pop();
};
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 2) this class has only pop and push
template<
class _Ty,
class _Predicate = Less<_Ty>, // comparator
class _Container = Array<_Ty // like std::vector

>

class PushPopPolicy : protected PriorityQueuePo licy<_Ty, _Predicate,
_Container >
{
typedef PriorityQueuePo licy<_Ty, _Predicate, _Container base;
public:
// common interface like std::priority_q ueue
void push(const _Ty& val){
base::push(val) ;
}

_Ty pop(){
if( base::empty()) throw exception;
_Ty val = base::top();
base::pop();
return val;
}
};
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//
template<
class _Ty,
class _Predicate = Less<_Ty>,
class _Container = Array<_Ty>
class _Policy = PriorityQueuePo licy<_Ty, _Predicate, _Container >

>

class PriorityQueue : public _Policy {};
///////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
Thanks

[acehreli@gmail.com]

Re: priority queue question

On Oct 28, 12:19 pm, vaclavp...@atla s.cz wrote:

Please write me what do you think about this :
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 1) first class is similar to std::priority_q ueue

    // common interface like std::priority_q ueue
    void push(const _Ty& val);
    _Ty& top();
    void pop();};

That interface allows to make those functions strongly exception-safe.

// 2) this class has only pop and push

    void push(const _Ty& val){
    _Ty pop(){
        if( base::empty()) throw exception;
         _Ty val = base::top();
       base::pop();
       return val;
    }};

That interface cannot be made strongly exception-safe because
base::pop() changes the state of the container before the top object
is handed over to the caller.

Then, if the copy constructor of _Ty throws during 'return val;' the
top object is lost. Herb Sutter's book Exceptional C++ and many other
sources cover this. Here is one:

http://www.boost.org/community/exception_safety.html

Ali

P.S. Any name that begins with an underscore followed by a capital
letter is reserved. Ty_ would be a better name.