Re: What's wrong ?

From:
Norbert Unterberg <nunterberg@newsgroups.nospam>
Newsgroups:
microsoft.public.vc.language
Date:
Thu, 09 Oct 2008 22:09:59 +0200
Message-ID:
<#NRYDskKJHA.1160@TK2MSFTNGP04.phx.gbl>
See below ...

Fil schrieb:

In the below I am trying:
- to save arrays of S into a pile (the Stack)
- and then to display each S.s (the only data member of S) wich is a string

#include <iostream>
#include <string>
#include "Stack.h"

struct S
{
    private:
        std::string s;
    public:
        S(std::string str){s=str;}
        void display()
        {
            std::cout << s << std::endl;
        }
};

int main()
{
    Stack iStack;
    S s1[]={S("a1"),S("b1"),S("c1")};
    S s2[]={S("a2"),S("b2"),S("c2")};
    S s3[]={S("a3"),S("b3"),S("c3")};
//push is a member function that insert the argument void* address at the
topof the pile
    iStack.push((void *)s1);
    iStack.push((void *)s2);
    iStack.push((void *)s3);
****
No need to cast to void*, every pointer converts to a void pointer without type
cast.
****

//I will cast the void* pointer returned from pop to a pointer to an array
of S
//The only thing I found is S** (I mean pointer to: (...)*, an array of S:
S*, so (S*)*)
    S** pS;
****
This is the problem. pop() returns the element that was pushed, which is S* and
not S**. This needs to be an S* pS.
****

//pop returns the top of the pile (void *) address and remove the element
from the pile. When all elements have been removed it returns 0.
    while ((pS=(S**)iStack.pop())!=0)
****
    while ((pS=(S*)iStack.pop())!=0)
****

     {
        for (int i=0; i<3; i++) //3 is the number of elements in each one of my
arrays
        {
//If pS is a pointer to an array of S then *pS is an array of S
            (*pS)[i].display();
****
   pS[i].display();
****

         }
    }
}


Norbert

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