Class Help

This is a discussion on Class Help within the C++ Programming forums, part of the General Programming Boards category; I'm currently working on my forest class for my forest fire simulation, but I've run into trouble. In one particular ...

  1. #1
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    Class Help

    I'm currently working on my forest class for my forest fire simulation, but I've run into trouble.
    In one particular spot, it wants to say grid is not declared.

    Here is a working implementation followed by the driver:
    Code:
    int forest::nextStatus(int i, int j) const
    {
      double rannum, z;
      rannum = static_cast<double>(rand())/RAND_MAX;
       z=(grid[i][j].getProbCatch()/grid[i][j].getWetness());
       
      if( (grid[i][j].getStatus()==live) && (rannum<z) && (grid[i+1][j].getStatus()==burning))  
      {
        return burning;
      }
      
      else if( (grid[i][j].getStatus()==live) && (rannum<z) && (grid[i-1][j].getStatus()==burning))
      {
        return burning;
      }
    
      else if( (grid[i][j].getStatus()==live) && (rannum<z) && (grid[i][j+1].getStatus()==burning))
      {
        return burning;
      }
    
      else if( (grid[i][j].getStatus()==live) && (rannum<z) && (grid[i][j-1].getStatus()==burning))
      {
        return burning;
      }
    
      else if( grid[i][j].getStatus()==burning )
      {
        return dead;
      }
    
      else if( grid[i][j].getStatus()==dead )
      {
        return dead;
      }
    
      else
      
    return live;
    }
    Code:
    void forest::applyNextStatus()
    {
      tree next_grid[FW][FH];
       int i, j, stat;
       
      for(int i=0; i<21; i++){
         for(int j=0; j<21; j++){
         
             next_grid[i][j]=grid[i][j];
         }
      }
    
    
       for(int i=1; i<20; i++){
          for(int j=1; j<20; j++){
    
              stat=nextStatus(i, j);
              next_grid[i][j].setStatus(stat);
          }
       }
    
      for(int i=0; i<21; i++){
         for(int j=0; j<21; j++){
    
              grid[i][j]=next_grid[i][j];
         }
      }
    }
    Driver:

    Code:
    b.applyNextStatus();
    However for this set, it is saying grid is not declared.
    Code:
    int regrowth(double growProb)
    {
        double rannum;
        rannum=static_cast<double>(rand())/RAND_MAX;
    
       for(int i=1; i<20; i++){
           for(int j=1; j<20; j++){
               if( (grid[i][j].getStatus()==dead) && (rannum<growProb)){
    
                  return live;
               }
               else{
    
                   return dead;
               }
           }
       }
    }
    Driver:
    Code:
    b.regrowth(rprob);

  2. #2
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    Where do you define grid? (ps; is regrowth supposed to be a member of forest?)

  3. #3
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    Here is the header file for the forest class:
    Code:
    #ifndef FOREST_H
    #define FOREST_H
    
    //Forest class declaration
    
    #include"tree.h"
    #include<iostream>
    using namespace std;
    
    #define FW 21
    #define FH 21
    
    class forest
    {
       private:
         tree grid[FW][FH];
    
       public:
         forest(); //default constructor
         void setGrid(int i, int j, double prob, int stat, double wet, int burn);
         int nextStatus(int i, int j) const;
         void applyNextStatus();
         bool isBurning();
         void lightning(double lightProb);
         int regrowth(double growProb);
    
       friend ostream& operator<<(ostream& out, forest&  b);
    };
    #endif //FOREST_H

  4. #4
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    You're missing something in the definition of regrowth (see scarecrow's ps for a hint).

  5. #5
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    Was the class specifier lost in translation, or is your code actually this way (sans forest:: ):
    Code:
    int forest::regrowth(double growProb)
    {
        double rannum;
        rannum=static_cast<double>(rand())/RAND_MAX;
    
       for(int i=1; i<20; i++){
           for(int j=1; j<20; j++){
               if( (grid[i][j].getStatus()==dead) && (rannum<growProb)){
    
                  return live;
               }
               else{
    
                   return dead;
               }
           }
       }
    }

  6. #6
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    Hah, there I go again making stupid simple mistakes.

    I forgot to put forest in front.

  7. #7
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    Shouldn't you have received an undefined ref. to regrowth??

  8. #8
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    Ok, it compiles, but it doesn't run anymore. Comment out the call to regrowth and the program runs fine.

    Here is the whole code for the driver loop:

    Code:
    while(b.isBurning()==true){
    
      tt=clock()+steppause*CLOCKS_PER_SEC;
      while(clock()<tt){}
      
      b.applyNextStatus();
      b.regrowth(rprob);
      cout<<b<<endl;
      
      
    }

  9. #9
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    Can you post the actual console output?
    Also, define "doesn't run anymore"...

  10. #10
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    Found my error. The problem lies in the function regrowth.

  11. #11
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    >> Shouldn't you have received an undefined ref. to regrowth??
    No, because the compiler thought it was a regular non-member function.

  12. #12
    C++まいる!Cをこわせ!
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    In other words, the compiler couldn't find the variable.
    If you tell the compiler that a variable exists but it doesn't (extern declarations, for example), THEN you will get a linking error. In other words, lie to the compiler.
    Quote Originally Posted by Adak View Post
    io.h certainly IS included in some modern compilers. It is no longer part of the standard for C, but it is nevertheless, included in the very latest Pelles C versions.
    Quote Originally Posted by Salem View Post
    You mean it's included as a crutch to help ancient programmers limp along without them having to relearn too much.

    Outside of your DOS world, your header file is meaningless.

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