Noobish problem

This is a discussion on Noobish problem within the C++ Programming forums, part of the General Programming Boards category; Code: #include <iostream> class myNodeList { private: struct myNode { char value; myNode * next; }; myNode * first; myNode ...

  1. #16
    tol
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    Fixed it, but need advice

    Code:
    #include <iostream>
    
    class myNodeList
    {
     private:
     struct myNode
     {
      char value;
      myNode * next;
     };
     myNode * first;
     myNode * index;
     public:
     myNodeList() : first(0),index(0){}
     ~myNodeList()
     {
      myNode * finger;
      finger=first;
      while(!(finger==0))
      {
       myNode * nullnext;
       nullnext=finger->next;
       delete finger;
       finger = nullnext;
      }
     }
     void addNode(char value)
     {
      myNode * newNode = new myNode();
      newNode->value = value;
      newNode->next = 0;
      if (first==0){first=newNode;}
      else 
      {
       myNode * finger;
       finger=first;
       while(!(finger->next==0)){finger=finger->next;}
       finger->next = newNode;
      }
     }
     void eachNode(void)
     {
      if (index==0){index=first;}
      else {index=index->next;}
     }
     char eachNode_getValue(void)
     {
      return index->value;
     }
     void printNodeList(void)
     {
      myNode * finger;
      finger=first;
      while(!(finger==0)){printf("%c",finger->value);finger=finger->next;};
     }
     int nodeCount(void)
     {
      myNode * finger;
      int count=0;
      finger=first;
      while(!(finger==0)){++count;finger=finger->next;}
      return count;
     }
    };
    int main(void)
    {
     myNodeList nodez;
     nodez.addNode('y');
     nodez.addNode('a');
     nodez.addNode('y');
     nodez.addNode('!');
     nodez.printNodeList();
     printf("\n");
     for (int index=0;index<nodez.nodeCount();++index)
     {
      nodez.eachNode();
      printf("%c.",nodez.eachNode_getValue());
     }
     printf("\n");
     system("PAUSE");
    }
    Works just peachy.

    Thanks for all the advice. The problem came because the FOR loop wasn't evaluating the eachNode along with the index, it was ignoring the part after the comma.

    However, I would like to know if there is a way I can squeeze the call to eachNode() up into the third bracket in FOR. It just looks cleaner to me, don't ask
    Last edited by tol; 07-21-2005 at 04:35 PM.

  2. #17
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    Well, you could do it like this. I don't know why, but I had to move the: int index
    outside the for-loop.
    Code:
     int index;
     for (index=0,nodez.eachNode();index<nodez.nodeCount();++index,nodez.eachNode())
    You're right, the problem wasn't calling eachNode() too many times, but that it wasn't initialized before printing the first node.

  3. #18
    tol
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    Right but

    This might seem overly picky, but wouldn't putting the int declaration inside the for loop technically be slightly superior because of scope?

  4. #19
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    Yes, if you can get it to compile. For some reason I couldn't get it to compile with it declared within the loop. But this would certainly be preferable.

    About an earlier question, you can turn on compiler warnings under Dev-C++ (gcc) with the -Wall option (under Tools -> Compiler Options).

  5. #20
    tol
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    Static Pointer problem

    Ok, I got the struct and class version working. All well and good on that, that will be good for what I am going to need it for. Now I am trying my other method just because I am interested, and because I am genuinely interested in messing around with this stuff for the sake of understanding, not just to get what I need right this second and cut out.

    Code:
    class Node {
     private:
     static Node * root; Node * next;
     char content;
     public:
     Node(char content)
     {
      if (root == 0)
      {
       root = this;
       next = NULL;
      }
      else
      {
       Node * finger = root;
       while(!(finger->next==0)){finger=finger->next;}
       finger->next=this;
      }
      this->content = content;
     }
    };
    Now I have a problem. Don't worry too much about the rest of the class, I just included that to make the context clear. What I want to do is make a class that will maintain just a single list of it's type of object. It lacks the flexibility of the way Swoopy showed me, but I am interested in it because I want this to be available when I don't require the separate structs(basically, when I don't need the ability for a program to have more than one list of the given object.)

    If I do it this way
    Code:
    static Node * root; Node * next;
    then it doesn't like root, because it is undefined. [Linker error] undefined reference to `Node::root'

    However, if I attempt to
    Code:
    static Node * root = NULL; Node * next;
    then it says
    4 ...\main.cpp invalid in-class initialization of static data member of non-integral type `Node*'

    This makes me think that it is not liking a class having a static self-pointer. Is there a way around this?

  6. #21
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    When using static member variables you declare it in the class declaration and initialize it outside the class variable:
    Code:
    //A.h
    //////////
    class A
    {
       static A * first;
    };
    
    A::A* first = NULL;
    You're only born perfect.

  7. #22
    tol
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    Unhappy More trouble ahead :)

    Thanks! The current state of my code is:

    Code:
    class Node 
    {
     private:
     static Node * root;static Node * index;Node * next;
     char content;
     public:
     Node(char content)
     {
      if (root == NULL)
      {
       root = this;
       next = NULL;
      }
      else
      {
       Node * finger = root;
       while(!(finger->next==NULL)){finger=finger->next;}
       finger->next=this;
      }
      this->content = content;
     }
     static int Count(void)
     {
      Node * finger;int count = 0;
      finger=root;
      while(!(finger->next==NULL)){finger=finger->next;++count;};
     }
    };
    Node::Node * root = NULL;
    Node::Node * index = NULL;
    I am still getting two [Linker error] undefined reference to `Node::root' errors in Dev C++ when I try to construct a node. Crazy, but I still think getting used to C++ will be more than worth it. Any idea why it's not liking this?

  8. #23
    Frequently Quite Prolix dwks's Avatar
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    Code:
    Node::Node * root = NULL;
    Do you mean
    Code:
    Node::root = NULL;
    dwk

    Seek and ye shall find. quaere et invenies.

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  9. #24
    tol
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    Thanks but

    The compiler seems to like that even less Still, thanks for the help anyhow.

  10. #25
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    Code:
    Node::Node * Node::root = NULL;

  11. #26
    tol
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    Thanks

    Wow, that seems to compile, thanks

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