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Need a little help

bhwdragon2012 (15)
For a past assignment I was asked to allow the user to input the name of a file.

Here was part of the code:
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void MakeArray(string filename);
int main()
{
	string filename; //Name of the file
	cout<<"Enter the filename: \n";
	cin>>filename;

        MakeArray(filename);


return 0;
}

void MakeArray(string filename)
{
	ifstream myfile; 
	myfile.open (filename.c_str());
	//took out the code that did not relate to opening the file
	myfile.close();  
}


I am wondering how you would go about telling the user that the file does not exit in the directory of the .exe file?
Last edited on
Stewbond (2827)
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ifstream myfile(filename.c_str());

if (!myfile)
    cout << filename.c_str() << " could not be opened." << endl;
bhwdragon2012 (15)
Thanks!
bhwdragon2012 (15)
EDIT:

Here is the full code:
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#include <iostream>
#include <string>
#include <fstream>

using namespace std;

//Global Variables
const int ROWS = 12;
const int COLS = 30;
const int BOARD_ROWS(10);
const int BOARD_COLS(28);
const char LIVE = 'X'; //life cells
const char DEAD = '.'; //dead cells
char NewBoard[ROWS][COLS];

//functions
void MakeArray(string filename, char board[][COLS]);
void GameBoard(char board[][COLS]);
void SwitchBoard (char board[][COLS]);
void NextState(char board[][COLS]);

int main()
{
	char board [ROWS][COLS];
	string filename; //Name of the file
	cout<<"Enter the filename: \n";
	cin>>filename;
	cout<<endl;

	//call functions
	MakeArray(filename, board);
	//start loop
	for (int l = 0; l<10; l++)
	{
		NextState(board);
		GameBoard(board);
		SwitchBoard(board);
	}
	//end loop

	//stop terminal window from quitting after programs ends
	char q;
	cin >> q;

	return 0;
}





void MakeArray(string filename, char board[][COLS])
{
	ifstream myfile;
	myfile.open (filename.c_str());
	if (!myfile)
	{
        cout << filename.c_str() << " File not found" << endl;
	}

	else
	{
    for (int r=0; r<ROWS; r++)
	{
		for (int c=0; c<COLS; c++)
		{
			myfile>>board[r][c];
		}
	}
	myfile.close();
	}
}
void GameBoard (char board[][COLS])
{
	for (int r=1; r<=ROWS-2; r++)
	{
		for (int c=1; c<=COLS-2; c++)
		{

			cout<<board[r][c];
		}
		cout<<endl;
	}
	cout<<endl;
}
void NextState (char board[][COLS])
{

	for (int r=0; r<ROWS; r++)
	{
		for (int c=0; c<COLS; c++)
		{

			int LiveCnt=0;
			if (board[r-1][c-1]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r-1][c]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r-1][c+1]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r][c-1]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r][c+1]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r+1][c-1]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r+1][c+1]==LIVE)
			{
				LiveCnt++;
			}
/*/
Rules:
1.	Any live cell with fewer than two live neighbours dies, as if caused by under-population.
2.	Any live cell with two or three live neighbours lives on to the next generation.
3.	Any live cell with more than three live neighbours dies, as if by overcrowding.
4.	Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.
/*/
			if (board[r][c] == LIVE && LiveCnt < 2) //rule 1
			{

				NewBoard[r][c]=DEAD;
			}
			else if (board[r][c]==LIVE && (LiveCnt==2 || LiveCnt==3))//rule 2
			{

				NewBoard[r][c]=LIVE;
			}
			else if (board[r][c]==LIVE && LiveCnt>3 ) //rule 3
			{

				NewBoard[r][c]=DEAD;
			}
			else if (board[r][c]==DEAD && LiveCnt==3) //rule 4
			{

				NewBoard[r][c]=LIVE;
			}
		}
	}



}
void SwitchBoard(char board[][COLS])
{

	for (int r=0; r<ROWS; r++)
	{
		for (int c=0; c<COLS; c++)
		{
			board[r][c]==NewBoard[r][c];
		}
	}

}


When I enter a wrong filename I get a bunch of weird symbols and messed of code in output?
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Enter the filename:
fibvjhsfib.txt

fibvjhsfib.txt File not found
  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ l╠F pFG ♦FG     (■(     H'
H'= h■( Ç⌠âv  =     ë⌠âv╛Z┘D
  X'= H'= z·EwR►Hw    $
H'= H'= ¿■( Ç⌠âv  =     ë⌠âv
┘D¶   \'= H'= z·EwR►Hw    $
ÿ■( ♦       >╖äù¿■(  ÷âv
  ╚╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv*Z┘D    ╚╕F     ►:A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ l╠F pFG ♦FG     (■(     H'
H'= h■( Ç⌠âv  =     ë⌠âv╛Z┘D
  X'= H'= z·EwR►Hw    $
H'= H'= ¿■( Ç⌠âv  =     ë⌠âv
┘D¶   \'= H'= z·EwR►Hw    $
ÿ■( ♦       >╖äù¿■(  ÷âv
  ╚╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv*Z┘D    ╚╕F     ►:A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ l╠F pFG ♦FG     (■(     H'
H'= h■( Ç⌠âv  =     ë⌠âv╛Z┘D
  X'= H'= z·EwR►Hw    $
H'= H'= ¿■( Ç⌠âv  =     ë⌠âv
┘D¶   \'= H'= z·EwR►Hw    $
ÿ■( ♦       >╖äù¿■(  ÷âv
  ╚╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv*Z┘D    ╚╕F     ►:A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ l╠F pFG ♦FG     (■(     H'
H'= h■( Ç⌠âv  =     ë⌠âv╛Z┘D
  X'= H'= z·EwR►Hw    $
H'= H'= ¿■( Ç⌠âv  =     ë⌠âv
┘D¶   \'= H'= z·EwR►Hw    $
ÿ■( ♦       >╖äù¿■(  ÷âv
  ╚╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv*Z┘D    ╚╕F     ►:A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ l╠F pFG ♦FG     (■(     H'
H'= h■( Ç⌠âv  =     ë⌠âv╛Z┘D
  X'= H'= z·EwR►Hw    $
H'= H'= ¿■( Ç⌠âv  =     ë⌠âv
┘D¶   \'= H'= z·EwR►Hw    $
ÿ■( ♦       >╖äù¿■(  ÷âv
  ╚╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv*Z┘D    ╚╕F     ►:A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ l╠F pFG ♦FG     (■(     H'
H'= h■( Ç⌠âv  =     ë⌠âv╛Z┘D
  X'= H'= z·EwR►Hw    $
H'= H'= ¿■( Ç⌠âv  =     ë⌠âv
┘D¶   \'= H'= z·EwR►Hw    $
ÿ■( ♦       >╖äù¿■(  ÷âv
  ╚╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv*Z┘D    ╚╕F     ►:A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ l╠F pFG ♦FG     (■(     H'
H'= h■( Ç⌠âv  =     ë⌠âv╛Z┘D
  X'= H'= z·EwR►Hw    $
H'= H'= ¿■( Ç⌠âv  =     ë⌠âv
┘D¶   \'= H'= z·EwR►Hw    $
ÿ■( ♦       >╖äù¿■(  ÷âv
  ╚╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv*Z┘D    ╚╕F     ►:A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ l╠F pFG ♦FG     (■(     H'
H'= h■( Ç⌠âv  =     ë⌠âv╛Z┘D
  X'= H'= z·EwR►Hw    $
H'= H'= ¿■( Ç⌠âv  =     ë⌠âv
┘D¶   \'= H'= z·EwR►Hw    $
ÿ■( ♦       >╖äù¿■(  ÷âv
  ╚╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv*Z┘D    ╚╕F     ►:A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ l╠F pFG ♦FG     (■(     H'
H'= h■( Ç⌠âv  =     ë⌠âv╛Z┘D
  X'= H'= z·EwR►Hw    $
H'= H'= ¿■( Ç⌠âv  =     ë⌠âv
┘D¶   \'= H'= z·EwR►Hw    $
ÿ■( ♦       >╖äù¿■(  ÷âv
  ╚╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv*Z┘D    ╚╕F     ►:A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ l╠F pFG ♦FG     (■(     H'
H'= h■( Ç⌠âv  =     ë⌠âv╛Z┘D
  X'= H'= z·EwR►Hw    $
H'= H'= ¿■( Ç⌠âv  =     ë⌠âv
┘D¶   \'= H'= z·EwR►Hw    $
ÿ■( ♦       >╖äù¿■(  ÷âv
  ╚╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv*Z┘D    ╚╕F     ►:A

georgewashere (244)
have you tried checking

if(!myFile.is_open())
bhwdragon2012 (15)
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#include <iostream>
#include <string>
#include <fstream>

using namespace std;

//Global Variables
const int ROWS = 12;
const int COLS = 30;
const int BOARD_ROWS(10);
const int BOARD_COLS(28);
const char LIVE = 'X'; //life cells
const char DEAD = '.'; //dead cells
char NewBoard[ROWS][COLS];

//functions
void MakeArray(string filename, char board[][COLS]);
void GameBoard(char board[][COLS]);
void SwitchBoard (char board[][COLS]);
void NextState(char board[][COLS]);

int main()
{
	char board [ROWS][COLS];
	string filename; //Name of the file
	cout<<"Enter the filename: \n";
	cin>>filename;
	cout<<endl;

	//call functions
	MakeArray(filename, board);
	//start loop
	for (int l = 0; l<10; l++)
	{
		NextState(board);
		GameBoard(board);
		SwitchBoard(board);
	}
	//end loop

	//stop terminal window from quitting after programs ends
	char q;
	cin >> q;

	return 0;
}





void MakeArray(string filename, char board[][COLS])
{
	ifstream myfile;
	myfile.open (filename.c_str());
	if (!myfile.is_open())
	{
        cout<< "File not found\n";
	}

	else
	{
    for (int r=0; r<ROWS; r++)
	{
		for (int c=0; c<COLS; c++)
		{
			myfile>>board[r][c];
		}
	}
	myfile.close();
	}
}
void GameBoard (char board[][COLS])
{
	for (int r=1; r<=ROWS-2; r++)
	{
		for (int c=1; c<=COLS-2; c++)
		{

			cout<<board[r][c];
		}
		cout<<endl;
	}
	cout<<endl;
}
void NextState (char board[][COLS])
{

	for (int r=0; r<ROWS; r++)
	{
		for (int c=0; c<COLS; c++)
		{

			int LiveCnt=0;
			if (board[r-1][c-1]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r-1][c]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r-1][c+1]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r][c-1]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r][c]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r][c+1]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r+1][c-1]==LIVE)
			{
				LiveCnt++;
			}
			if (board[r+1][c+1]==LIVE)
			{
				LiveCnt++;
			}
/*/
Rules:
1.	Any live cell with fewer than two live neighbours dies, as if caused by under-population.
2.	Any live cell with two or three live neighbours lives on to the next generation.
3.	Any live cell with more than three live neighbours dies, as if by overcrowding.
4.	Any dead cell with exactly three live neighbours becomes a live cell, as if by reproduction.
/*/
			if (board[r][c] == LIVE && LiveCnt < 2) //rule 1
			{

				NewBoard[r][c]=DEAD;
			}
			else if (board[r][c]==LIVE && (LiveCnt==2 || LiveCnt==3))//rule 2
			{

				NewBoard[r][c]=LIVE;
			}
			else if (board[r][c]==LIVE && LiveCnt>3 ) //rule 3
			{

				NewBoard[r][c]=DEAD;
			}
			else if (board[r][c]==DEAD && LiveCnt==3) //rule 4
			{

				NewBoard[r][c]=LIVE;
			}
		}
	}



}
void SwitchBoard(char board[][COLS])
{

	for (int r=0; r<ROWS; r++)
	{
		for (int c=0; c<COLS; c++)
		{
			board[r][c]==NewBoard[r][c];
		}
	}

}


output:
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Enter the filename:
h.txt

File not found
  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ \╠F pFG ♦FG     (■(     H'
H'W h■( Ç⌠âv  W     ë⌠âv!╥╛¼
  X'W H'W z·EwR►Hw    $
H'W H'W ¿■( Ç⌠âv  W     ë⌠âv
╛¼¶   \'W H'W z·EwR►Hw    $
ÿ■( ♦       │╣╖c¿■(  ÷âv
  ╕╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv╡╥╛¼    ╕╕F      :A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ \╠F pFG ♦FG     (■(     H'
H'W h■( Ç⌠âv  W     ë⌠âv!╥╛¼
  X'W H'W z·EwR►Hw    $
H'W H'W ¿■( Ç⌠âv  W     ë⌠âv
╛¼¶   \'W H'W z·EwR►Hw    $
ÿ■( ♦       │╣╖c¿■(  ÷âv
  ╕╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv╡╥╛¼    ╕╕F      :A

  (↨G ¶ƒG h↕G ¶ƒG ▄²( ∞²( h↕
(↨G ¶ƒG ♠       ♠   ►   ☺
@ \╠F pFG ♦FG     (■(     H'
H'W h■( Ç⌠âv  W     ë⌠âv!╥╛¼
  X'W H'W z·EwR►Hw    $
H'W H'W ¿■( Ç⌠âv  W     ë⌠âv
╛¼¶   \'W H'W z·EwR►Hw    $
ÿ■( ♦       │╣╖c¿■(  ÷âv
  ╕╕F ╝■( Bñâv¿☻ìvⁿ■( ╥⌠â
Ä◄ävb◄äv╡╥╛¼    ╕╕F      :A

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This code works:
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#include <iostream>
#include <string>
#include <fstream>

using namespace std;

//Global Variables
const int ROWS = 12;
const int COLS = 30;
const int BOARD_ROWS(10);
const int BOARD_COLS(28);
const char LIVE = 'X'; //life cells
const char DEAD = '.'; //dead cells
char NewBoard[ROWS][COLS];

//functions
void MakeArray(string filename);

int main()
{

	string filename; //Name of the file
	cout<<"Enter the filename: \n";
	cin>>filename;
	cout<<endl;

	//call functions
	MakeArray(filename);
	//start loop

	//end loop

	//stop terminal window from quitting after programs ends
	char q;
	cin >> q;

	return 0;
}





void MakeArray(string filename)
{


	ifstream myfile;
	myfile.open (filename.c_str());
	if (!myfile.is_open())

        cout<< "File not found\n";

	myfile.close();

}


but it doesn't work with the full game of life code.

Also im using code blocks
Last edited on
Stewbond (2827)
Okay, so you are finding that the file was not found. This worked okay. The problem is that your program still continued to run with uninitialized values. These values are not initialized because the file was not there.

You have two options:
1. Loop the prompt that asks the user to enter a filename that exists until the file actually exists.
2. Quite the program if an invalid filename was entered.

To do this, it might be a good idea to have MakeArray return true if everything failed: 
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bool MakeArray(string filename, char board[][COLS])
{
	ifstream myfile;
	myfile.open (filename.c_str());
	if (!myfile) return true;

    for (int r=0; r<ROWS; r++)
	{
		for (int c=0; c<COLS; c++)
		{
			myfile>>board[r][c];
		}
	}
	myfile.close();

	return false;
}


For option 1 you would do this in your main:
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while (true)
{
	cout<<"Enter the filename: \n";
	cin>>filename;
	cout<<endl;

	//call functions
	if (!MakeArray(filename, board)) break; // Exit only if the file was opened, otherwise, ask again.
}


For option 2 you would do this in your main:
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cout<<"Enter the filename: \n";
cin>>filename;
cout<<endl;

//call functions
if (MakeArray(filename, board))
{
	cout << "Bad file entered, now exiting..." << endl;
	return 1;
}
//The rest of your code only runs if a valid file was entered. Otherwise the program stops.
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