Re: return references from templates

From:

LR <lruss@superlink.net>

Newsgroups:

comp.lang.c++

Date:

Thu, 24 Mar 2011 22:24:32 -0400

Message-ID:

<4d8bfce5$0$8739$cc2e38e6@news.uslec.net>

Ruben Safir wrote:

I have a snippet of code that looks like this

template<class unk>
NODE<unk> * const &LIST<unk>::find(const unk& search) const {
    NODE<unk> * index;
    if(_at_front == NULL){
        return _at_front;
    }

    index = _at_front;

    while(index){
        if( search == index->value())
            return index;
        index= index->next();
    }
    return NULL;
}

Despite the fact that index points to new allocated memory, it won't
compile

|| In file included from linklist_main.cpp:1:
|| linklist.h: In member function ???CHAINLIST::NODE<unk>* const&
CHAINLIST::LIST<unk>::find(const unk&) const [with unk = int]???:
linklist_main.cpp|140| instantiated from here
linklist.h|291| warning: reference to local variable ???index??? returned

I think Victor Bazarov's question elsethread about why you are returning
a reference is a good one.

What does next() return? If it returns a reference to a pointer then
maybe you can store a pointer to the previous element in the list and
return prev->next() or something. There will likely be some problems
_at_front.

I suspect that "return NULL;" which is going to get another warning is
going to be a little more difficult to solve if you want to continue to
return a reference. Perhaps a static data member or a static member
function somewhere for this.

I think I would also like to ask, is there some reason you can't use
std::list?

LR