Struct within Class, Problem with OVERLOADING OPERATORS
 

So the assignment is to create a Sorted Linked List, not doubly, and not using a tail. I am using a SortedListNode Struct in the private area of the SortedList class. I think this is causing problems. I have the logic, and I was on the verge of succeeding, but then I got stuck with this. I never had to overload == or < or > for a Struct item, within a Class. (and one main requirement is that I do not use a helper function within my insert or remove functions)

The SortedList will eventually accept a string word, and compare it (while doing insert) to the cur one, to determain where to put it. (for this I am converting it to char, and then doing strcmpi)
but the main problem right now is that I think I don't know how to overload the Struct within the Class as a friend. I know there is more than one option, and not use a friend, but I will probably encounter the same problem with the syntax.

Here is my code:

#include <iostream>

#include <cstring>

#include <string>

#include <cstddef>//for NULL

using namespace std;



class SortedList

{

private:

        

        struct SortedListNode

        {

                string word;//holds within the word in the node

                SortedListNode* next;//pointer to next node

        };

        

        int size;//number of nodes (words) in the sorted list

        

        SortedListNode* head;//pointer to the sorted linked list of words



        //optional: SortedListNode* tail;//pointer to th

        

        //SortedListNode* locatePosition(string aWord, 



public:

        

        SortedList();

        

        ~SortedList();



        bool sortedIsEmpty()const;



        int sortedGetLength()const;

        

        void sortedInsert(string newWord);



        void sortedRemove(string oldWord); 

        

        void sortedRetrieve(int index, string& theWord)const;



    friend bool operator==(const SortedListNode& wordA, const SortedListNode& wordB);

};



SortedList::SortedList(): size(0), head(NULL)

{}



SortedList::~SortedList() 

{

        delete head;//and not to forget, use size to walk through the sorted list and delete all Nodes

}



bool SortedList::sortedIsEmpty() const

{

        return size;//if size is 0, it returns 0, if size is any other number- it returns 1

}



int SortedList::sortedGetLength()const

{

        return size;

}



void SortedList::sortedInsert(string newWord)

{

        SortedListNode* newNodePtr = new SortedListNode;

        newNodePtr->next = NULL;

        newNodePtr->word = newWord;

        

        if(size==0)//insertion at beginning of List

        {

                newNodePtr->next = head;

                head = newNodePtr;

                size++;

        }

        else//insertion not at beginning of list

        {

                SortedListNode* prev = NULL;

                SortedListNode* cur = head;

                //for(; cur->next != NULL; prev = cur, cur = cur->next);//for(int i = size; i <= size; i++)

                //{ 

                        //if (newNodePtr->word == cur->word); //throw exception- already present



                        //if (newNodePtr->word > cur->word) 

                        //{

                        //        if(cur->next = NULL);// then its the last one on list- insert here 

                //        }

                        //else

                        //{

                                //advance by 1 more node

                //        }

                        

                        //if newNodePtr->word < cur->word then prev->next = newNodePtr and newNodePtr->next = cur (insert new node here)

                



        

                //}

        }

}



bool SortedList::operator==(const SortedListNode*& wordA, const SortedListNode*& wordB)

{

        string first = wordA->word;

        string second = wordB->word;

        const char* forFirst = first.c_str();

        const char* forSecond = second.c_str();

        return strcmpi(forFirst, forSecond);

}

Re: Struct within Class, Problem with OVERLOADING OPERATORS
 

1) get rid of strcmpi() C function. See my version of the == operator below.
2) add

#include <algorithm>

for the transform() function

3) The friend function is not part of the class, so it has to reference the SortedListNode by SortedList::SortedListNode

#include <iostream>

#include <cstring>

#include <string>

#include <cstddef>//for NULL

#include <algorithm>

using namespace std;



class SortedList

{

private:

        

        struct SortedListNode

        {

                string word;//holds within the word in the node

                SortedListNode* next;//pointer to next node

        };

        

        int size;//number of nodes (words) in the sorted list

        

        SortedListNode* head;//pointer to the sorted linked list of words



        //optional: SortedListNode* tail;//pointer to th

        

        //SortedListNode* locatePosition(string aWord, 



public:

        

        SortedList();

        

        ~SortedList();



        int sortedIsEmpty()const;



        int sortedGetLength()const;

        

        void sortedInsert(string newWord);



        void sortedRemove(string oldWord); 

        

        void sortedRetrieve(int index, string& theWord)const;



// Note:  if you want to pass pointers to this function

// then change it to * instead of &, but not both.

    friend bool operator==(const SortedList::SortedListNode& wordA, const SortedList::SortedListNode& wordB); 

};



SortedList::SortedList(): size(0), head(NULL)

{}



SortedList::~SortedList() 

{

        delete head;//and not to forget, use size to walk through the sorted list and delete all Nodes

}



int SortedList::sortedIsEmpty() const

{

    return size;//if size is 0, it returns 0, if size is any other number- it returns 1

}



int SortedList::sortedGetLength()const

{

        return size;

}



void SortedList::sortedInsert(string newWord)

{

        SortedListNode* newNodePtr = new SortedListNode;

        newNodePtr->next = NULL;

        newNodePtr->word = newWord;

        

        if(size==0)//insertion at beginning of List

        {

                newNodePtr->next = head;

                head = newNodePtr;

                size++;

        }

        else//insertion not at beginning of list

        {

                SortedListNode* prev = NULL;

                SortedListNode* cur = head;

                //for(; cur->next != NULL; prev = cur, cur = cur->next);//for(int i = size; i <= size; i++)

                //{ 

                        //if (newNodePtr->word == cur->word); //throw exception- already present



                        //if (newNodePtr->word > cur->word) 

                        //{

                        //        if(cur->next = NULL);// then its the last one on list- insert here 

                //        }

                        //else

                        //{

                                //advance by 1 more node

                //        }

                        

                        //if newNodePtr->word < cur->word then prev->next = newNodePtr and newNodePtr->next = cur (insert new node here)

                



        

                //}

        }

}





// Note:  See my node in the class above.

bool operator==(const SortedList::SortedListNode& wordA, const SortedList::SortedListNode& wordB)

{

    string a = wordA.word;

    string b = wordB.word;

    transform(a.begin(), a.end(), a.begin(), toupper);

    transform(b.begin(), b.end(), b.begin(), toupper);

    return a == b ? true : false;

}

Re: Struct within Class, Problem with OVERLOADING OPERATORS
 

I tried, but it says:
1>MSVCRTD.lib(crtexe.obj) : error LNK2019: unresolved external symbol _main referenced in function ___tmainCRTStartup
1>C:\Users\Owner\Documents\Visual Studio 2008\Projects\Project1\testing\Debug\testing.exe : fatal error LNK1120: 1 unresolved externals

Re: Struct within Class, Problem with OVERLOADING OPERATORS
 

Hey, its your code, not mine. Where is the main() function ??? Didn't your teacher tell you that every c++ program needs a main() function.

Re: Struct within Class, Problem with OVERLOADING OPERATORS
 

oh my god! LOL I have it, but I forgot to put it in when I used your solution. Im checking it, and soon ill post. THANKS!!!!!