Overloading == and < operator

This is a discussion on Overloading == and < operator within the C++ Programming forums, part of the General Programming Boards category; Ok I have all of my code written, but I am not sure about overloading the == and < operators. ...

  1. #1
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    Overloading == and < operator

    Ok I have all of my code written, but I am not sure about overloading the == and < operators. I keep getting an error that says no match for operator < in 's1<s3'

    here is the code...I have tried adding
    Code:
    friend Song::operator==(const Song &s)
    but that doesn't work either.
    Code:
    //song.h
    #ifndef SONG_H
    #define SONG_H
    #include <stdlib.h>
    #include <iostream>
    #include <ostream>
    #include <string>
    #include "BobCatPod.h"
    using namespace std;
    
    
    class Song
    {
      
       public:
          Song();
          Song(string , string , int ); // constructor
          void setSize(int s);
          int getSize(); // access or
          void setTitle (string t);
          string getTitle();
          void setArtist (string a);
          string getArtist();
          void addSong (int);
          friend ostream& operator<<(ostream & os, const Song & s);
          
       private:
          string title;    //dynamic allocation
          string artist;
          int size;
    };
    #endif
    Code:
    // poddriver.cpp
    
    //Adapted from Roger Priebe
    //CS2308 11/17/08
    
    #include <stdlib.h>
    #include <iostream>
    #include "BobCatPod.h"
    #include "song.h"
    
    using namespace std;
    
    int main()
    {
        
        Song s1("Frank Sinatra", "My way", 14);
        Song s2("Beatles", "Act Naturally", 5);
        Song s3;
        
        BobCatPod p(256);
        BobCatPod q(512);
        BobCatPod r(25);
    
    
        cout << "pod p" << endl << p << endl;
        cout << "pod q, size 512 exceeds max, should be reset to 256 " << endl
             << q << endl;
        cout << "pod r, size should be 25 " << endl << r << endl;
    
    
        cout << "Song 1" << s1 << endl;
        cout << "Song 2" << s2 << endl;
        cout << "Song 3" << s3 << endl;
    
        s3.setArtist("Buck Owens");
        s3.setTitle("Act Naturally");
        s3.setSize(20);
    
        cout << "Song 3 updated " << s3 << endl;
        cout << "Artist 1 (Frank Sinatra)  " << s1.getArtist() << endl;
        cout << "Title 2 (Act Naturally)  " << s2.getTitle() << endl;
    //    s1.setSize(7);
    //    cout << "Size 1 (7) " << s1.getSize() << endl;
    
    //test relational operators
    
        if (s1 < s3 ) cout << endl << "s1 < s3" << endl;
          else cout << endl << "s1 >= s3" << endl;
        if (s1 == s2) cout << endl << "s1 == s2" << endl;
          else cout << endl << "s1 != s2"  << endl;
        
    // test addnode
        cout << "add song 1, size 14 " << r.addSong(s1) << endl;  
        cout << "   memory left = "  << r.getRemainingMemory() <<endl;
        cout << "add song 2, size 5 " << r.addSong(s2)<< endl; 
        cout << "   memory left = "  << r.getRemainingMemory() << endl;
        cout << "add song 3, size 20 should fail " << r.addSong(s3) <<endl;
        cout << "   memory left = "  << r.getRemainingMemory() << endl;
      
        s3.setSize(2);
        cout << "Size 3 (2) " << s3.getSize() << endl;
        cout << "add song 3, size 2 should succeed " << r.addSong(s3) 
             << "   memory left = "  << r.getRemainingMemory() << endl;
    
    
    // test output
        cout << r << endl;
    
    //test delete
    
        r.removeSong(s1);
        cout << r << endl;
        r.removeSong(s3);
        cout << r << endl;
    
        cout << "Total Memory = "<< r.getTotalMemory() << endl;
    
    
    
    
    
        return 0;
    }
    Thanks

  2. #2
    C++ Witch laserlight's Avatar
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    Looking at all your accessor functions, you probably can declare them as free functions:
    Code:
    bool operator==(const Song& lhs, const Song& rhs);
    bool operator<(const Song& lhs, const Song& rhs);
    Oh, and please remove that using directive from your header file.
    C + C++ Compiler: MinGW port of GCC
    Version Control System: Bazaar

    Look up a C++ Reference and learn How To Ask Questions The Smart Way

  3. #3
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    Ok here is everything. why won't it work? I am getting so frustrated with this I feel like I have a puzzle with all the edge pieces missing.

    Code:
    //song.h
    #ifndef SONG_H
    #define SONG_H
    #include <stdlib.h>
    #include <iostream>
    #include <ostream>
    #include <string>
    #include "BobCatPod.h"
    
    
    
    class Song
    {
      
       public:
          Song();
          Song(string , string , int ); // constructor
          void setSize(int s);
          int getSize(); // access or
          void setTitle (string t);
          string getTitle();
          void setArtist (string a);
          string getArtist();
          void addSong (int);
          friend ostream& operator<<(ostream & os, const Song & s);
          bool operator==(const Song& lhs, const Song& rhs);
          bool operator<(const Song& lhs, const Song& rhs);
       private:
          string title;    //dynamic allocation
          string artist;
          int size;
    };
    #endif
    Code:
    // file song.cpp
    #include "song.h"
    #include "BobCatPod.h"
    
     ostream & operator << ( ostream & os, Song & s)
     {
          os << s.getTitle();
          os  << s.getArtist();
          os << s.getSize();
          return os;
     }
    //constructor
    Song::Song ()
    {
        title=" ";
        artist=" ";
        size = 0;
    }
    Song::Song(string a, string t, int s) // constructor
    {
        size = s;
        title = t;
        
        artist = a ;
        
    }
    //accessor for name
    string Song :: getTitle()
    {
          return title;
    }
    //mutator
    void Song :: setTitle (string t)
    {
         title = t;
         
    }
    string Song :: getArtist()
    {
          return artist;
    }
    //mutator
    void Song :: setArtist (string a)
    {
         artist = a;
         
    }
    void Song::setSize(int s)
    {
        size = s;
    }
    int Song::getSize()
    {
        return size;
    }
    Code:
    //BobCatPod.h
    
    //Specification files for the SongList class
    
    #ifndef BOBCATPOD_H
    #define BOBCATPOD_H
    #include "song.h"
    
    
    
    class BobCatPod
    {
          
          private:
          struct SongNode
          {
                 Song s;                  //value in this node
                 SongNode *next;
          
                             
          };
          
          SongNode *head;
          static const int MAX_MEMORY = 256;
          
          
          public:
                 int totalMemory;
                 int remainingMemory;
                 
                 
                 //Constructor
                 BobCatPod();
    
                     
                 //Linked list operations
                 BobCatPod::BobCatPod(int i);
                 bool isFull ( ) const;
                 int addSong (Song s);
                 int removeSong (Song s);
                 void showSongList ();
                 int getTotalMemory();
                 int getRemainingMemory();
                 friend ostream & operator<<(ostream & os, const BobCatPod & i);
                 
                 
                 //Destructor
                 ~BobCatPod();
    
    };
    #endif
    Code:
    //BobCatPod.cpp
    #include "song.h"
    #include "BobCatPod.h"
    
    
    
    BobCatPod::BobCatPod()
    {
         head = NULL;
         
    }
    
    bool BobCatPod::isFull ( ) const
    {
         if (totalMemory > MAX_MEMORY)
         {
          
                    return true;
         }
    }
    
    BobCatPod::BobCatPod(int i)  
    {
        
        if( i <= MAX_MEMORY)
            remainingMemory = i;    
        else
            remainingMemory = MAX_MEMORY;
    }
    
    int BobCatPod::addSong(Song t)
    {
          if (isFull ())
         {
                    return 0;
         }
         SongNode *newSong = new SongNode;     //a new node
         
        
         
         // Allocate a new node and stor num there.
         
         newSong->s = t; 
         head = newSong;
         newSong->next = NULL;
         totalMemory++;
        
         return 1;
    }
    
    
    int BobCatPod::removeSong( Song t )
    {
         if (isFull ())
         {
                    totalMemory--;
                    return 1;
         }
         else     
         return 1;
    }
     
    void BobCatPod::showSongList( )
    {
         SongNode *n;
         cout<<endl;
     
         for( n = head ; n != NULL ; n = n->next )
            cout<<endl<<n->s;
    }
    
    int BobCatPod::getTotalMemory()
    {
        Song t;
        totalMemory = t.getSize();
        return totalMemory;
    }
    
    int BobCatPod::getRemainingMemory()
    {
        
        remainingMemory = MAX_MEMORY - totalMemory;
        return remainingMemory;
    }
    Code:
    // poddriver.cpp
    
    //Adapted from Roger Priebe
    //CS2308 11/17/08
    
    #include <stdlib.h>
    #include <iostream>
    #include "BobCatPod.h"
    #include "song.h"
    
    using namespace std;
    
    int main()
    {
        
        Song s1("Frank Sinatra", "My way", 14);
        Song s2("Beatles", "Act Naturally", 5);
        Song s3;
        
        BobCatPod p(256);
        BobCatPod q(512);
        BobCatPod r(25);
    
    
        cout << "pod p" << endl << p << endl;
        cout << "pod q, size 512 exceeds max, should be reset to 256 " << endl
             << q << endl;
        cout << "pod r, size should be 25 " << endl << r << endl;
    
    
        cout << "Song 1" << s1 << endl;
        cout << "Song 2" << s2 << endl;
        cout << "Song 3" << s3 << endl;
    
        s3.setArtist("Buck Owens");
        s3.setTitle("Act Naturally");
        s3.setSize(20);
    
        cout << "Song 3 updated " << s3 << endl;
        cout << "Artist 1 (Frank Sinatra)  " << s1.getArtist() << endl;
        cout << "Title 2 (Act Naturally)  " << s2.getTitle() << endl;
    //    s1.setSize(7);
    //    cout << "Size 1 (7) " << s1.getSize() << endl;
    
    //test relational operators
    
        if (s1 < s3 ) cout << endl << "s1 < s3" << endl;
          else cout << endl << "s1 >= s3" << endl;
        if (s1 == s2) cout << endl << "s1 == s2" << endl;
          else cout << endl << "s1 != s2"  << endl;
        
    // test addnode
        cout << "add song 1, size 14 " << r.addSong(s1) << endl;  
        cout << "   memory left = "  << r.getRemainingMemory() <<endl;
        cout << "add song 2, size 5 " << r.addSong(s2)<< endl; 
        cout << "   memory left = "  << r.getRemainingMemory() << endl;
        cout << "add song 3, size 20 should fail " << r.addSong(s3) <<endl;
        cout << "   memory left = "  << r.getRemainingMemory() << endl;
      
        s3.setSize(2);
        cout << "Size 3 (2) " << s3.getSize() << endl;
        cout << "add song 3, size 2 should succeed " << r.addSong(s3) 
             << "   memory left = "  << r.getRemainingMemory() << endl;
    
    
    // test output
        cout << r << endl;
    
    //test delete
    
        r.removeSong(s1);
        cout << r << endl;
        r.removeSong(s3);
        cout << r << endl;
    
        cout << "Total Memory = "<< r.getTotalMemory() << endl;
    
    
    
    
    
        return 0;
    }
    I feel like i am just plugging holes in a sinking ship and I am running out of fingers.

    Thanks for all the help I appreciate it

  4. #4
    C++ Witch laserlight's Avatar
    Join Date
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    Location
    Singapore
    Posts
    21,430
    No, free functions, so they are not part of the class.

    However, all your get member functions should be declared const.
    C + C++ Compiler: MinGW port of GCC
    Version Control System: Bazaar

    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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