problem passing cstring, incompatible types

I'm writing a singly linked list class and I have just started. I'm having problems with

Code:

---

(*startPointer).name = name;

---

Here is my code:

main.cpp

Code:

---

#include <iostream>
#include <cstring>
#include "LinkedList.h"

using namespace std;

int main()
{
    cout << "Enter your name:" << endl;
    char myName[20];
    cin.getline(myName, 20, '\n');
    return 0;
}

---

LinkedList.cpp

Code:

---

#include <cstdlib>
#include <iostream>
#include <cstring>
#include "../include/LinkedList.h"

//default constructor
LinkedList::LinkedList() : startPointer(NULL), length(0)
{

}

//destructor
LinkedList::~LinkedList()
{

}

bool LinkedList::createNode(char name[])
{
    if(startPointer == NULL)
    {
        startPointer = new aNode;//aNode is a struct
        (*startPointer).name = name;
        std::cout << "Should be the same: " << (*startPointer).name <<std::endl;
    }
   
    return true;
}

---

LinkedList.h

Code:

---

#ifndef LINKEDLIST_H
#define LINKEDLIST_H

class LinkedList
{
    public:
        LinkedList();
        ~LinkedList();
        void addToList();
        bool createNode(char name[]);

    private:
        unsigned int length;
        struct aNode
        {
            char name[20];
            aNode *next;
        };
        aNode *startPointer;

};
#endif // LINKEDLIST_H

---

In constructor 'LinkedList::LinkedList()':
warning: 'LinkedList::startPointer' will be initialized after
warning: 'unsigned int LinkedList::length'
warning: when initialized here
In member function 'bool LinkedList::createNode(char*)':
error: incompatible types in assignment of 'char*' to 'char [20]'
warning: no return statement in function returning non-void

You cannot just assign the pointer like that because (*startPointer).name is an array, and you cannot assign to an array. You need to copy the string, e.g.,

Code:

---

strcpy(startPointer->name, name);

---

Now, why are you not using std::string so you can concentrate on learning how to implement a linked list?

I fixed this and now I'm getting a bunch of errors about the constructor, destructor and createNode(char name[]) having multiple definitions.

First you need to answer laserlight's question.
Then you need to post your update source code.
Also, NULL should be nullptr.

Quote:

---

Originally Posted by Elysia

Also, NULL should be nullptr.

---

Feel free to ignore this if it does not work for you, probably until sometime next year (hopefully) when the next version of the C++ standard is published.

I'd say that unless you have very specific requirements, you should be using a compiler that supports it, eg Visual Studio 2010 Express or newest GCC.

main

Code:

---

#include <iostream>
#include <cstring>
#include "src\LinkedList.cpp"

using namespace std;

int main()
{
    cout << "Enter your name:" << endl;
    char myName[20];
    cin.getline(myName, 20, '\n');
    return 0;
}

---

LinkedList.cpp

Code:

---

#include <cstdlib>
#include <iostream>
//#include <cstring>
#include <string.h>
#include "..\include\LinkedList.h"

//default constructor
LinkedList::LinkedList() : startPointer(NULL), length(0)
{

}

//destructor
LinkedList::~LinkedList()
{

}

bool LinkedList::createNode(char name[])
{
    if(startPointer == NULL)
    {
        startPointer = new aNode;//aNode is a struct
        strcpy((*startPointer).name, name);//can't just assign with = because can't do arr1[]=arr2[]
        std::cout << "Should be the same: " << (*startPointer).name <<std::endl;
    }

    return true;
}

---

LinkedList.h

Code:

---

#ifndef LINKEDLIST_H
#define LINKEDLIST_H

class LinkedList
{
    public:
        LinkedList();
        ~LinkedList();
        void addToList();
        bool createNode(char name[]);//creates a node at end of list

    private:
        unsigned int length;
        struct aNode
        {
            char name[20];
            aNode *next;
        };
        aNode *startPointer;

};

#endif // LINKEDLIST_H

---

H:\code_blocks_workspace\ThisWillWork\src\..\inclu de\LinkedList.h||In constructor 'LinkedList::LinkedList()':|
H:\code_blocks_workspace\ThisWillWork\src\..\inclu de\LinkedList.h|19|warning: 'LinkedList::startPointer' will be initialized after|
H:\code_blocks_workspace\ThisWillWork\src\..\inclu de\LinkedList.h|13|warning: 'unsigned int LinkedList::length'|
H:\code_blocks_workspace\ThisWillWork\src\LinkedLi st.cpp|8|warning: when initialized here|
H:\code_blocks_workspace\ThisWillWork\src\..\inclu de\LinkedList.h||In constructor 'LinkedList::LinkedList()':|
H:\code_blocks_workspace\ThisWillWork\src\..\inclu de\LinkedList.h|19|warning: 'LinkedList::startPointer' will be initialized after|
H:\code_blocks_workspace\ThisWillWork\src\..\inclu de\LinkedList.h|13|warning: 'unsigned int LinkedList::length'|
H:\code_blocks_workspace\ThisWillWork\src\LinkedLi st.cpp|8|warning: when initialized here|
obj\Debug\main.o||In function `LinkedList':|
H:\code_blocks_workspace\ThisWillWork\src\LinkedLi st.cpp|8|multiple definition of `LinkedList::LinkedList()'|
obj\Debug\src\LinkedList.o:H:\code_blocks_workspac e\ThisWillWork\src\LinkedList.cpp|8|first defined here|
obj\Debug\main.o||In function `LinkedList':|
H:\code_blocks_workspace\ThisWillWork\src\LinkedLi st.cpp|8|multiple definition of `LinkedList::LinkedList()'|
obj\Debug\src\LinkedList.o:H:\code_blocks_workspac e\ThisWillWork\src\LinkedList.cpp|8|first defined here|
obj\Debug\main.o||In function `~LinkedList':|
H:\code_blocks_workspace\ThisWillWork\src\LinkedLi st.cpp|14|multiple definition of `LinkedList::~LinkedList()'|
obj\Debug\src\LinkedList.o:H:\code_blocks_workspac e\ThisWillWork\src\LinkedList.cpp|14|first defined here|
obj\Debug\main.o||In function `~LinkedList':|
H:\code_blocks_workspace\ThisWillWork\src\LinkedLi st.cpp|14|multiple definition of `LinkedList::~LinkedList()'|
obj\Debug\src\LinkedList.o:H:\code_blocks_workspac e\ThisWillWork\src\LinkedList.cpp|14|first defined here|
obj\Debug\main.o:H:\code_blocks_workspace\ThisWill Work\src\LinkedList.cpp|20|multiple definition of `LinkedList::createNode(char*)'|
obj\Debug\src\LinkedList.o:H:\code_blocks_workspac e\ThisWillWork\src\LinkedList.cpp|20|first defined here|
||=== Build finished: 10 errors, 6 warnings ===|


I'm more familiar with cstrings and when I tried to use std::string I got some errors, so I'll change that latter thanks.

Don't include .cpp files.

Quote:

---

Originally Posted by Elysia

Don't include .cpp files.

---

I've had a great deal of difficulty understanding this. How does this make sense when LinkedList.cpp includes LinkedList.h? Wouldn't including LinkedList.h leave out LinkedList.cpp since it doesn't include it (where as LinkedList.cpp includes LinkedList.h)?

Why does it work like this? In otherwords, why is what I did wrong?

Each source file is compiled separately, then combined to form the program.
It makes sense to have declarations, which are going to be used in several source files, to reside in headers. Then you can copy and paste the contents of those headers into your source files. That is what happens when you include a header.

Got it. Just curious why my compiler gives me these warnigns:

H:\code_blocks_workspace\ThisWillWork\src\..\inclu de\LinkedList.h||In constructor 'LinkedList::LinkedList()':|
H:\code_blocks_workspace\ThisWillWork\src\..\inclu de\LinkedList.h|19|warning: 'LinkedList::startPointer' will be initialized after|
H:\code_blocks_workspace\ThisWillWork\src\..\inclu de\LinkedList.h|13|warning: 'unsigned int LinkedList::length'|
H:\code_blocks_workspace\ThisWillWork\src\LinkedLi st.cpp|8|warning: when initialized here|
||=== Build finished: 0 errors, 3 warnings ===|

Because in your class definition, you have (in order):
unsigned int length;
ANode* StartPointer;
But in your initializer list, you initialize them in reverse order. You might think that the compiler will initialize the values in the order it seems them in the initializer list, but that is not correct.
In fact, it will initialize them in the order they appear in the your class definition.
That is why your compiler is warning you.

Also, you should try substituting NULL with nullptr. If you have C++0x support, this should compile and be better than NULL.

Quote:

---

Originally Posted by Elysia

Because in your class definition, you have (in order):
unsigned int length;
ANode* StartPointer;
But in your initializer list, you initialize them in reverse order. You might think that the compiler will initialize the values in the order it seems them in the initializer list, but that is not correct.
In fact, it will initialize them in the order they appear in the your class definition.
That is why your compiler is warning you.

---

Got it.

Quote:

---

Originally Posted by Elysia

Also, you should try substituting NULL with nullptr. If you have C++0x support, this should compile and be better than NULL.

---

I was unable to get this to work.

Code:

---

#include <cstdlib>
#include <iostream>
#include <string.h>
#include "..\include\LinkedList.h"

LinkedList::LinkedList() : length(0), startPointer(nullptr)
{

}

LinkedList::~LinkedList()
{

}

bool LinkedList::createNode(char name[])
{
    if(startPointer == nullptr)
    {
        startPointer = new aNode;        strcpy((*startPointer).name, name);[]
        std::cout << "Your name is: " << (*startPointer).name <<std::endl;
    }

    return true;
}

---

I'm using MinGW 4.5