problem in the context

This is a discussion on problem in the context within the C++ Programming forums, part of the General Programming Boards category; Can anyone explain to me why this code is not working? Code: #include <iostream> using namespace std; class linkedListclass { ...

  1. #1
    Registered User
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    Jan 2008
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    problem in the context

    Can anyone explain to me why this code is not working?

    Code:
    #include <iostream>
    
    using namespace std;
    
    
    class linkedListclass {
    public:
    
    void code(int length)  {
    		
    		x=length;
    		if (x !=4)
    			cout << "The code is short" << endl;
    		else
    			cout << " goooood you got it" << endl;		
    }
    
    
    
    /*  void printlist()  {
        cout << "current node is " << dvalue << endl;
        if (next != NULL)
          next->printlist();
        else
          cout << "\n\n";
      }*/
    
    private:
      int x;
    
    };
    
    
    int main()  {
    	int newvalue
    	int length;
    	cout << "Insert a code of 12 characters:";
    	cin >> newvalue;
    	length = newvalue.length();	
    	
      	linkedListclass first;
    
      first= new linkedListclass(length);
    
    /*  cout << "The value is " << first->getdvalue() << endl;
    
      first->addbehind(45);
      first->printlist();
    
      first->addinfront(10);
      first->printlist();*/
    
      return 0;
    }

  2. #2
    and the Hat of Guessing tabstop's Avatar
    Join Date
    Nov 2007
    Posts
    14,185
    1. No semicolon after int newvalue;
    2. You can't read characters into an int;
    3. You can't take the length of an int.

  3. #3
    Use this: dudeomanodude's Avatar
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    Let me ask you: what is "next" in this code? It's not defined.

    "next" typically refers to the next element of the list. it's a pointer, that will be necessary for things like traversing the list and creating new elements of the list.

    I know creating a linked-list is one of those re-inventing the wheel type problems you're faced with in school, but an understanding of how a linked-list works is a must if you wish to continue your journey.

    First ask, what am i creating a list of? people? sure, let's create a linked-list of people.

    Code:
    #include <iostream>
    using namespace std;
    
    class Person{
    
        public:
    
            // Notice "next(0)"...
            // next is set to zero or NULL so we know where the end of our list is.
            Person(string n, string o, int a) : name(n), occupation(o), age(a), next(0) {};
            
            string get_name(){ return name; };
            string get_occupation(){ return occupation; };
            int get_age(){ return age; };
            
            // Because next is private, we can access it like so:
            Person * get_next(){ return next; };
            
            // And if we'd like to create new Persons, let's add this:
            void add_person(string n, string o, int a){ next = new Person(n,o,a); };
    
        private:
    
            string name;
            string occupation;
            int age;
    
            // This will allow us to make our list:
            Person * next;
    };
    
    int main(){
    
        // Let's declare a Person pointer "head" here that will be the first person in our list.
        Person * head;
    
        // Right now, no Person exists, so let's actually create the first Person like this:
        head = new Person("Bob", "Programmer", 35);
        
        // Now let's create another person
        // We'll need another "general purpose" pointer:
        Person * p = head;
        
        // With our add_person() function, a new person will be created in the next position:
        p->add_person("Alice", "HairDresser", 26);
        
        // But what if we don't always want to create a new Person? What if we need to do that later?
        // We can always get to the last person our list with a loop like this:
        p = head;
        
        while(p->get_next() != 0) // 0 indicates the end of the list
        {
        	p = p->get_next();
        }
        
        // Now let's go ahead and add one more person:
        p->add_person("Jerry", "BarTender", 28);
        
        // To display our list in the command window:
        // Initialize p back to the beginning:
        p = head;
    
        // Traverse the list showing the different people:
        while(p != 0){
        	
        	cout << p->get_name() << " " << p->get_occupation() << " " << p->get_age() << endl;
        	
        	// Advance p to the next person until we get to the end:
        	p = p->get_next();
        }
        
        return 0;
    }
    This is by no means a complete tutorial on linked lists, in-fact, this list I've created here is not very practical for many reasons. But it does illustrate some of the aspects of creating a linked-list.

    Try creating your own lists of things, and remember pointers only POINT. that's all they do. study this, and other data structures.

  4. #4
    Use this: dudeomanodude's Avatar
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    Also, before Laserlight scolds you, clean up your code a bit. That means have a consistent indentation scheme, spacing between certain lines of code, etc. In general, just make your code easier to read, especially if you post it here for other people to sift through...

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