Datafile
Hej,Jeg skal lave en text file med foelgende integers
2 13 48 90 23 44 88 45 97 32 48 97 67 453
Jeg lavede derfor en i notepad og kaldte den "datafile", men det virker ikke. Er der en der kan gennemskue hvad jeg goer galt og hvordan jeg kan faa loest dette proble. Jeg har pastet mit program saa i har mulighed for at compile det. Der mangler jo saa textfilen. Det er paakraevet at jeg bruger:
#define DATAFILE "datafile.txt"
Paa forhaand tak!
#include <iostream.h> // for input and output statements
#include <fstream.h> // for reading from and writing to a file
#define DATAFILE "datafile.txt" // the file containing integer numbers
const int MAX_LEN = 50; // maximum number of elements
const char BLANK = ' '; // used for a dummy character
const int DONT_CARE = 0; // used for a dummy integer variable
const int SO_MANY_CHARS = 100; // to be used with ignor() to skip blanks
enum message_type {OPENING,CLOSING,UNKNOWN_CHAR, NOT_FOUND,POSITION_IN_LIST,WARNING};
//==========================================================================================
// prototypes
//==========================================================================================
void print_message(message_type sttm, char ch, int val, int pos);
void fill_list(ifstream &infile, int list[], int& len);
void print_list (const int list[], int len);
void get_menu_item (char& ans);
void get_value (int& val);
int find_position(const int list[],int len, int val);
void delete_value (int list[],int& len,int index);
//******************************************************************************************
// main()
//******************************************************************************************
void main()
{
int list[MAX_LEN]; // the list for holding up to MAX_LEN numbers
int length; // number of elements of the array
int value; // value to be deleted from the list entered by the user
int index; // the index to the value to be deleted in the list
char answer; // answer to the query enterd by the user
ifstream infile; //input file stream
infile.open(DATAFILE,ios::in|ios::nocreate); //open datafile for reading
if (infile.fail())
cout<<"*** Can't open the file**"<<endl;
else
{
print_message(OPENING,BLANK,DONT_CARE,DONT_CARE);
fill_list (infile,list,length);
print_list(list, length);
do
{
get_menu_item(answer);
switch (answer)
{
case 'd': get_value (value);
index= find_position (list, length, value);
if (index<0) // value not found
print_message(NOT_FOUND,BLANK, value,DONT_CARE );
else
{
print_message(POSITION_IN_LIST,BLANK, value,index+1); //add one to index to be user friendly
delete_value (list, length, index);
print_list(list, length);
}
break;
case 'q': print_message(CLOSING,BLANK,DONT_CARE,DONT_CARE);
break;
default: print_message (UNKNOWN_CHAR,answer,DONT_CARE,DONT_CARE);
break; //not necessary but a good habit
}//switch
} while (answer != 'q');
infile.close();
}
}
//******************************************************************************************
// print_message()
// This function writes messages on the screen.
//******************************************************************************************
void print_message(/*in*/ message_type sttm, //type of message
/*in*/ char ch, //used with UNKNOWN_CHAR message
/*in*/ int val, //used with NOT_FOUND and POSITION_INLIST message
/*in*/ int pos) //used with POSITION_INLIST message
{
switch (sttm)
{
case UNKNOWN_CHAR: cout<<"=======> Sorry I don't understand what "<<'"'<<ch<<'"'<< " means\n";
break;
case NOT_FOUND: cout<<"=======> Sorry "<<val<<" is not in the list\n";
break;
case OPENING: cout<<"This program deletes a number form a given list for you. "
<<"Here is the list (read from a file):\n";
break;
case CLOSING: cout<<"***********************************************************\n";
cout<<" Thanks for choosing our program and bye now.\n";
cout<<"***********************************************************\n";
break;
case POSITION_IN_LIST:
cout<<"The first occurance of the value "<<"("<<val<<")"<< " is at position ";
cout<<pos<<endl;
break;
case WARNING: cout<<"----Warning---> The file contains more than " << MAX_LEN<<" elements. ";
cout<<"Only the first "<< MAX_LEN<<" elements will be processed.\n";
break;//UNNECESSARY BUT A GOOD HABIT
}
}
//******************************************************************************************
// fill_list()
// This function fills up the array with numbers in the file. If the file contains
// more than MAX_LEN numbers only the first MAX_LEN numbers will be processed.
//******************************************************************************************
void fill_list(/* in*/ ifstream &infile,//contains the numbers
/*out*/ int list[], //for holding the numbers
/*out*/ int& len) //length of the list
{
int buffer;
len =0;
infile >> buffer;
while (infile && len< MAX_LEN)
{
list[len]=buffer;
len++;
infile >>buffer;
}
//if (infile)
}
//******************************************************************************************
// print_list()
// This function prints the elements of the array.
//******************************************************************************************
void print_list (/* in*/ const int list[], // the list
/*in*/ int len) // number of elements stored in the array
{
int curr_index;
for (curr_index =0; curr_index<len; curr_index++)
{
cout << list [curr_index]<<endl;
}
}
//******************************************************************************************
// get_menu_item()
// This function gets a menu item from the user.
//******************************************************************************************
void get_menu_item (/*out*/ char& ans) // d for delete and q for quit
{
cout<< "Would you like to [d]elete a value or [q]uit the program?";
cin >> ans;
cin.ignore(SO_MANY_CHARS,'\n'); //ignore the rest of the line
cout<<endl;
}
//******************************************************************************************
// get_value()
// This function gets an integer number from the user.
//******************************************************************************************
void get_value (/*out*/ int& val) // an integer number to be deleted from the list
{
cout<< "Enter the value you wish to delete: ";
cin >> val;
cin.ignore(SO_MANY_CHARS,'\n'); //ignore the rest of the line
cout<<endl;
}
//******************************************************************************************
// find_position()
// This function finds the postion of the value in the list, if found. if the value is not
// in the list it returns -1.
//******************************************************************************************
int find_position(/*in*/ const int list[], // the list to be searched
int len, // the lenght of the list
int val) // the vlaue to be looked up
{
bool found=false;
int curr_pos=0;
while ((len< MAX_LEN) && (!found))
{
if (list[curr_pos]== val)
found=true;
else
curr_pos++;
}
if (found)
return curr_pos;
else
return -1;
return 0; // this statement must be replaced by the body
// of the function
}
//******************************************************************************************
// delete_value()
// This function deletes the value from the list. Note that it is assumed the value is in
// the list.
//******************************************************************************************
void delete_value (/*out*/ int list[], //the list to be modified
/*out*/ int& len, // length of the list
/*in*/ int index) // the index of the value to be deleted
{
int pos;
int curr_pos;
int last_index;
curr_pos= pos;
last_index=len-1;
while (curr_pos <last_index -1)
{
list[curr_pos]=list[curr_pos + 1];
}
len++;
}
