Polymorphism Help

This is a discussion on Polymorphism Help within the C++ Programming forums, part of the General Programming Boards category; The error is due to the semi-colon after forest(). It is declared in the header file, but adding the semi-colon ...

  1. #16
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    The error is due to the semi-colon after forest(). It is declared in the header file, but adding the semi-colon is redeclaring it in the implementation.

  2. #17
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    Ok, I'm nearly finished. I'm trying to create the forest using the array of tree pointers.

    Code:
    //-------------------------------------------------------------------------
    //Default Forest Constructor
    //-------------------------------------------------------------------------
    
    forest::forest()
    {
      
      for(int i=0; i<21; i++){
           for(int j=0; j<21; j++){
    
               int x=i&#37;2;
               int y=j%2;
    
    	     if ( i == 0 || i == 20 || j == 0 || j == 20 ) { 
                 
                   grid[i][j] = new tree;
                 }
                 else if( x==0 || y==0 ){
    
                   grid[i][j] = new pine;
                 }
                 else{
    
                   grid[i][j] = new oak;
                 }
            }
       }
    }
    Here is the compiler error:
    Code:
    forest.cpp: In constructor ‘forest::forest()’:
    forest.cpp:30: error: expected type-specifier before ‘pine’
    forest.cpp:30: error: cannot convert ‘int*’ to ‘tree*’ in assignment
    forest.cpp:30: error: expected `;' before ‘pine’
    forest.cpp:34: error: expected type-specifier before ‘oak’
    forest.cpp:34: error: cannot convert ‘int*’ to ‘tree*’ in assignment
    forest.cpp:34: error: expected `;' before ‘oak’

  3. #18
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    Did you #include Oak.h and Pine.h in the forest.cpp file?

  4. #19
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    Nope, I forgot to include them.

    Now I have the following error:
    Code:
    /home/ryan/Desktop/C++_Lab/Final_Project/Part K/forest.cpp:32: undefined reference to `pine::pine()'
    /home/ryan/Desktop/C++_Lab/Final_Project/Part K/forest.cpp:36: undefined reference to `oak::oak()'
    /home/ryan/Desktop/C++_Lab/Final_Project/Part K/forest.cpp:32: undefined reference to `pine::pine()'
    /home/ryan/Desktop/C++_Lab/Final_Project/Part K/forest.cpp:36: undefined reference to `oak::oak()'

  5. #20
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    Did you add Pine.cpp and Oak.cpp to your project (or makefile or command line or whatever you are using to build)?

  6. #21
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    I'm stunned that one of the first things they taught in the course was not how to compile, link, and run a program.

  7. #22
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    Quote Originally Posted by medievalelks View Post
    I'm stunned that one of the first things they taught in the course was not how to compile, link, and run a program.
    Sounds like the course isn't the greatest in the world. It's supposed to be an Intro to C++ course, but they're trying to teach polymorphism and inheritance without teaching the STL properly (by the look of it - they're just bringing the entire STL into the global namespace) or any basic C/C++ fundimentals (includes, compiling, linking)...

  8. #23
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    Nope, I also left them out of the make.

    Program runs fine now.

    I'm finished!

    Thanks everyone for the help!
    Ryan

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