someone can see this and someone can't see the magic on STL vector

sanzilla (59)
hi all, first of all I am very new to the C++ programming and the STL
programming. But I did this exercise on C++ STL vectors.

This is the exercise that I have did .
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#include <iostream.h>
#include <vector.h>


struct vector_element
{
       int a ;
       int b ;
       vector_element( int aa , int bb )
       {
                       a = aa ;
                       b = bb;
        }
};

    // push create a empty vector
    vector<vector_element>* vector_1 = new vector<vector_element> ;
    

int main(int argc, char *argv[])
{
    

    // let's fill it up
    for ( int i = 0 ; i < 100 ; i++ )
    {
        // create a new vector element and initialize it
        vector_element *prt_vector_element = new vector_element ( i , i+1);  
        // Then we have to just push it
        vector_1->push_back ( *prt_vector_element);
    }
    
    // Just getting an iterator to the Vector
    vector<vector_element>::iterator iterator_;
       
    // now we are getting the elements out from the vector
    for ( iterator_ = vector_1->begin() ;iterator_ != vector_1->end() ; iterator_++)
         cout << ( * iterator_ ).a << (*iterator_).b << endl;
    system("PAUSE");
    return EXIT_SUCCESS;
}



and the magic is this code is not working .... and get an access violation exception under the windows .....

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#include <cstdlib>
#include <iostream>
#include <fstream>
#include <vector>
#include <windows.h>
using namespace std ;
/* these is line struct */
struct line
{
      
       int length ;
       char *  str1  ;
       
       line ( char str[] , int length )
       {
            // create the new arreay
            str = new char [length+1] ;
            
            // then copy it
            for ( int i = 0 ; i < length ; i++ )
                str1[i] = str [i];
            str [length ] = 0;
            this->length = length ;
       }
};

/* this is the lines structure then */
struct  lines 
{
       vector<line> * lines_vector ;
       int a ;
       // the constructor will create get a char* and torkernize it into the 
       //   lines and make line objects and push them into the vector.
 
       char * getline (int line ) 
       {
            // this will output line number 'line'
            //line & requested_line ;
            //requested_line =  lines_vector[line];
            return (lines_vector->operator[] (line) ).str1  ;
       }
       
       int get_num_lines () 
       {
           return lines_vector->size();
       }
 
       lines ( char * str , int length ) 
       {
            // thus we are using the lines_vector thus initialize it
            lines_vector = new vector<line>;
                     
             //lines_vector = new vector<line>;
             int current_position = 0 ;
             int current_line_position = 0 ;
             char *current_line = new char[200] ; // we are assuming that the current line is not
             // greater than the 200 characters... however this is NUTS
             for ( ; current_position < length ; current_position++)
             {
                 // if we current char '\n' then
                 if ( str[current_position] == '\n' )
                 {
                         current_line [current_line_position] = 0;
                         line * new_line = new line ( current_line , current_line_position + 1  );
                         cout << "current line is " << current_line << "current length is : " << strlen ( current_line)  << endl;
                         lines_vector->push_back (  *new_line );       
                         cout << "debug -- line 2" << endl ;   
                         current_line_position = 0  ;          
                 }else{
                         current_line [ current_line_position  ] = str [current_position];
                         current_line_position++ ;
                 }
      
             }      
            
       }
};

/* This is the Model of our window */
struct Model 
{
       int first_print_line   ;
       TEXTMETRIC tm ;
       int cyCaps   ;
       
       // this will holds the number of lines on the screen
       int num_lines  ;
       int num_lines_in_file  ;
       // the current y size of the screen 
       int window_height  ;
       int window_width  ;
       
       // this is the lines 
       lines * lines_object ;
       
       char * getline ( int line )
       {
            return  lines_object->getline(line);
       }
       
       Model (HWND hwnd ) 
       {
             RECT rect ; 
             
             // Get Device Context
             HDC hdc = GetDC ( hwnd ) ;
             //GetTextMetrics ( hdc , &tm );
             GetClientRect ( hwnd , &rect ) ;
             window_height = rect.bottom - rect.top ;
             window_width = rect.right - rect.left ;
             // then calculate the cyCaps from it;
             cyCaps = tm.tmHeight + tm.tmExternalLeading ;           
             // then we can know how many lines that we can actually 
             // print 
             num_lines = window_height / cyCaps ;
             ReleaseDC ( hwnd , hdc ) ; 
             /* This function just open the file and fill the lines 
               Structure 
             */
             first_print_line = 0 ;
             char*  str  = new char [2001];
             // just open the file and read it to the str array 
             ifstream infile ;
             infile.open( "reading.txt" ) ;
             
             /*
             MessageBox(NULL , "File open" , infile.is_open() ? "File has been Opened" : "file is not open " , MB_OK );
             //infile>>.get ( str , 2000) ;
             infile.read ( str , 2000);
           
             // debug ---
             char * str11  = new char [200];
             for ( int i = 0 ; i < 100 ; i++ )
                 str11[i] = str[i];
             str11[99] ='\n'; 
             cout << str11 << endl;  
             // debug --
             */
             
             
             lines_object = new lines ( str , 2001 ) ;
             num_lines_in_file = lines_object->get_num_lines();
       }      
     
       // THE WM_SIZE mesage should call this function.
       void WM_PAINT_callback ( HWND hwnd )
       {
             RECT rect ;
             GetClientRect ( hwnd , &rect ) ;
             window_height = rect.bottom - rect.top ;
             window_width = rect.right - rect.left ; 
                          // then we can know how many lines that we can actually 
             // print 
             num_lines = window_height / cyCaps ;
       }
} * window_model ;


int main()
{
   // create a model 
   char * myString = "This is the case\nThis is you\nand you gonna to be a \ncool\nthis is it\nit is that\n";
   lines*  new_lines = new lines ( myString , strlen ( myString));
   
   cout <<( new_lines->getline ( 3));
   system("PAUSE");
   return 0;
}


And the funny thing is for the second program the DEV C++ IDE debugger is not working for the code. I am not a pro in C++ programming , so I'm not telling that this is a bug in the C++ IDE.

In the second program these are the lines that getting the exception ....Even
the debugger is not working .. so then I try the source code cout tags to debug
and watch variables.... 
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                        current_line [current_line_position] = 0;
                         line * new_line = new line ( current_line , current_line_position + 1  );
                         cout << "current line is " << current_line << "current length is : " << strlen ( current_line)  << endl;
                         lines_vector->push_back (  *new_line );       
                         cout << "debug -- line 2" << endl ;   
                         current_line_position = 0  ;


actually telling the line is
lines_vector->push_back( *new_line);
But the problem is same thing is wroking nice on first,
jsmith (5804)
The problem in your first code is that you can't write the code

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// push create a empty vector
vector<vector_element>* vector_1 = new vector<vector_element> ;


outside of any function.
anders43 (125)
Why don't you just declare the vector as 

 
 
vector<vector_element> vector_1;


and in your loop just create vector_elements on the stack

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vector_element ve;

vector_1.push_back(ve);


since the contents of your struct doesn't have any ptrs etc.
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