C / C++ / MFC

17-Feb-06 15:35

Hello,

I am trying to understand recursion by using the following example.

   <br />
#include <iostream><br />
#include <iomanip><br />
<br />
using namespace std;<br />
<br />
unsigned long factorial( unsigned long ); // function prototype<br />
//-------------------------------------------------------------------------<br />
int main()<br />
{<br />
   // Loop 4 times. During each iteration, calculate factorial( i ) and display result.<br />
   for ( int i = 0; i <= 4; i++ )<br />
   {<br />
	  cout << "\n i = " << i << endl;<br />
	  cout << endl << setw( 2 ) << i << "! = " << factorial( i ) << endl;<br />
   }<br />
   return 0;  // indicates successful termination<br />
<br />
} // end main<br />
//-------------------------------------------------------------------------<br />
// recursive definition of function factorial<br />
unsigned long factorial( unsigned long number )<br />
{<br />
   // base case<br />
   if ( number <= 1 )  <br />
   {<br />
      return 1;<br />
   }<br />
   // recursive step<br />
   else  <br />
   {<br />
	  cout << endl << "number = " << number << "    factorial(number - 1) = " << factorial(number - 1) <br />
		   << "    number * factorial(number - 1) = " << number * factorial( number - 1 ) << endl;          <br />
      return number * factorial( number - 1 );<br />
   }<br />
} // end function factorial<br />
//-------------------------------------------------------------------------<br />
/*<br />
output:<br />
<br />
 i = 0<br />
<br />
 0! = 1<br />
<br />
 i = 1<br />
<br />
 1! = 1<br />
<br />
 i = 2<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
 2! = 2<br />
<br />
 i = 3<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
number = 3    factorial(number - 1) = 2    number * factorial(number - 1) = 6<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
 3! = 6<br />
<br />
 i = 4<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
number = 3    factorial(number - 1) = 2    number * factorial(number - 1) = 6<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
number = 3    factorial(number - 1) = 2    number * factorial(number - 1) = 6<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
number = 4    factorial(number - 1) = 6    number * factorial(number - 1) = 24<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
number = 3    factorial(number - 1) = 2    number * factorial(number - 1) = 6<br />
<br />
number = 2    factorial(number - 1) = 1    number * factorial(number - 1) = 2<br />
<br />
 4! = 24<br />
Press any key to continue<br />
*/<br />

I do understand that when i = 0, the base case is true, therefore 1 is returned. 0! = 1

When i = 1, the base case is true and 1 is returned. 1! = 1

When i = 2, the base case is not true, so number * factorial( number - 1 ) is returned, which is 2 * factorial( 1 ). 2 * 1 = 2. 2 is returned. 2! = 2

At this point, I have a question. The next line says i = 3. Then it says number = 2. How does number become 2 if i = 3?

Thanks,
Eric

Michael Dunn17-Feb-06 16:22

17-Feb-06 16:22

The recursive calls have to complete before the output can be sent to cout. So what you're seeing is the output from the deepest recursive call first.

--Mike--
Visual C++ MVP Cool | :cool:

LINKS~! Ericahist | NEW!! PimpFish | CP SearchBar v3.0 | C++ Forum FAQ

ericelysia17-Feb-06 16:36

17-Feb-06 16:36

Hasn't the output already been sent to cout? The program already output 2! = 2 and i = 3.

At the point in the program where i = 3 is output, doesn't that signify the beginning of a new iteration?

Thanks,
Eric

ericelysia17-Feb-06 18:54

17-Feb-06 18:54

OK, I still don't get it. I changed the code a little to make the invocations easier to see.

<br />
#include <iostream><br />
#include <iomanip><br />
using namespace std;<br />
<br />
unsigned long factorial( unsigned long ); // function prototype<br />
//-------------------------------------------------------------------------<br />
int count = 0;<br />
<br />
int main()<br />
{  <br />
   // Loop 2 times. During each iteration, calculate factorial( i ) and display result.<br />
   for ( int i = 0; i <= 2; i++ )<br />
   {<br />
	  cout << "\n i = " << i << endl;<br />
	  cout << endl << setw( 2 ) << i << "! = " << factorial( i ) << endl;<br />
	  cout << endl << "--------------------------------------------" << endl;<br />
   }<br />
   return 0;  // indicates successful termination<br />
<br />
} // end main<br />
//-------------------------------------------------------------------------<br />
// recursive definition of function factorial<br />
unsigned long factorial( unsigned long number )<br />
{  <br />
   count++;<br />
   cout << endl << "factorial was invoked for the " << count << " time "<br />
        << "   number = " << number << endl;<br />
<br />
   // base case<br />
   if ( number <= 1 )  <br />
   {<br />
	  cout << endl << "number <= 1" << endl;<br />
      return 1;<br />
   }<br />
   // recursive step<br />
   else  <br />
   {<br />
	  cout << endl << "number = " << number <br />
		   << "    factorial(number - 1) = " << factorial(number - 1) <br />
		   << "     " <br />
		   << number  << " * " << factorial( number - 1 ) << " = " <br />
		   << number * factorial( number - 1 ) << endl;    <br />
		         <br />
      return number * factorial( number - 1 );<br />
   }<br />
} // end function factorial<br />
//-------------------------------------------------------------------------<br />

OUTPUT:

<br />
<br />
 i = 0<br />
<br />
factorial was invoked for the 1 time    number = 0<br />
<br />
number <= 1<br />
<br />
 0! = 1<br />
<br />
--------------------------------------------<br />
<br />
 i = 1<br />
<br />
factorial was invoked for the 2 time    number = 1<br />
<br />
number <= 1<br />
<br />
 1! = 1<br />
<br />
--------------------------------------------<br />
<br />
 i = 2<br />
<br />
factorial was invoked for the 3 time    number = 2<br />
<br />
factorial was invoked for the 4 time    number = 1<br />
<br />
number <= 1<br />
<br />
factorial was invoked for the 5 time    number = 1<br />
<br />
number <= 1<br />
<br />
factorial was invoked for the 6 time    number = 1<br />
<br />
number <= 1<br />
<br />
number = 2    factorial(number - 1) = 1     2 * 1 = 2<br />
<br />
factorial was invoked for the 7 time    number = 1<br />
<br />
number <= 1<br />
<br />
 2! = 2<br />
<br />
--------------------------------------------<br />
Press any key to continue<br />
*/<br />

Please walk me through the following:

<br />
 i = 2<br />
<br />
factorial was invoked for the 3 time    number = 2<br />
<br />
factorial was invoked for the 4 time    number = 1<br />
<br />
number <= 1<br />
<br />
factorial was invoked for the 5 time    number = 1<br />
<br />
number <= 1<br />
<br />
factorial was invoked for the 6 time    number = 1<br />
<br />
number <= 1<br />
<br />
number = 2    factorial(number - 1) = 1     2 * 1 = 2<br />
<br />
factorial was invoked for the 7 time    number = 1<br />
<br />
number <= 1<br />
<br />
 2! = 2<br />

Thanks!

David Crow18-Feb-06 7:13

David Crow

18-Feb-06 7:13

It appears that you are calling factorial() three times within itself (one for the algorithm itself, and two for the cout statements). With all of those cout statements, that may be leading to the confusion.

"The greatest good you can do for another is not just to share your riches but to reveal to him his own." - Benjamin Disraeli

Jeremy Thornton18-Feb-06 9:10

Jeremy Thornton

18-Feb-06 9:10

If you are trying to track the stages of recursion with the cout line then I suggest that you minimise your confusion by calling your recursive function just ONCE and storing the result to use in your cout line and to return, I think that this will you help dissect what is going on?

Good luck I´m sure it will just click and you will go "Ah!" Smile | :)

ericelysia20-Feb-06 3:37

20-Feb-06 3:37

OK, thanks to all of the great feedback, I have a better understanding about recursion.

I am now attempting to apply it and I have come across a problem that I can't seem to pinpoint.

I have written the "eight queens" program, but for some reason, I get an infinite loop. I think my base case is ok. Can someone help me figure out what I am doing wrong here?

Thanks in advance,
Eric

<br />
#include <iostream><br />
<br />
using namespace std;<br />
<br />
<br />
const int BOARD_SIZE = 8;<br />
<br />
// function prototypes<br />
void fillBoard( int [], int, int );<br />
bool noConflict( int [], int, int );<br />
void printBoard( int [], int );<br />
<br />
//--------------------------------------------------------------<br />
<br />
// main method<br />
int main()<br />
{<br />
	int chessboard[ BOARD_SIZE ];				// represents a chessboard with 8 rows (0-7)<br />
	int column = 0;				<br />
	int count = 0;						// keeps track of the count<br />
<br />
	fillBoard( chessboard, column, count );	// invokes fillBoard function to start filling the chessboard<br />
<br />
	return 0;	// indicates sucessful termination<br />
} // end main method<br />
<br />
//--------------------------------------------------------------<br />
<br />
// fillBoard method<br />
void fillBoard( int board[ BOARD_SIZE ], int c, int cnt )<br />
{<br />
	for( int r = 0; r <= 7; r ++ )			// for every row on the board<br />
	{<br />
		board[ c ] = r;						// assign the value of row to the column<br />
	<br />
<br />
		if( noConflict( board, r, c ) )		// if there is not a conflicting queen<br />
		{<br />
			if( c == 7 )					// if it is the last column<br />
			{<br />
				printBoard( board, cnt);	// output the board<br />
			}<br />
<br />
			else				<br />
			{<br />
				fillBoard( board, c + 1, cnt );	// else recursively invoke fillBoard for the next column<br />
			}<br />
		}<br />
	}<br />
} // end fillBoard method<br />
<br />
//--------------------------------------------------------------<br />
<br />
// noConflict method<br />
bool noConflict( int board[ BOARD_SIZE ], int r, int c )<br />
{<br />
	for( int col = c - 1; col >= 0; col-- )		// for each column on the board<br />
	{<br />
		if( board[ col ] == r				// checks horizontally to the left<br />
		 || board[ col ] == r + c - col		// checks diagonally moving down and to the left<br />
		 || board[ col ] == r + col - c )	// checks diagonally moving up and to the left<br />
		{<br />
			return false;	// there is a conflict<br />
		}<br />
		else<br />
		{<br />
			return true;	// there is not a conflict<br />
		}<br />
	}<br />
	return true;			// there is not a conflict<br />
} // end noConflict method<br />
<br />
//-------------------------------------------------------------<br />
<br />
// printBoard method<br />
void printBoard( int board [ BOARD_SIZE ], int cnt )<br />
{<br />
	cout << "Count = " << ++cnt << endl;	// output the count<br />
<br />
	for( int r = 0; r <= 7; r++ )			// for each row on the board<br />
	{<br />
		for( int c = 0; c <= 7; c++ )		// for each column on the board<br />
		{<br />
			if( board[ c ] == r )			// if the value of the column index is equal to the value of the row<br />
			{	<br />
				cout << "Q ";				// place a queen on that position<br />
			}<br />
<br />
			else<br />
			{<br />
				cout << "- ";				// else place a "dash" for an empty square on the board<br />
			}<br />
		}<br />
		cout << endl;<br />
	}<br />
	cout << endl;<br />
} // end printBoard method<br />
<br />
//-------------------------------------------------------------<br />

WinInet FtpPutFile

rbrad1234517-Feb-06 15:21

rbrad12345

17-Feb-06 15:21

Hello everyone,

I'm writing a simple class to handle FTP SEND of a file from a WinCE 4.2 box. I'm having some trouble with the FtpPutFile call. I've tried several FTP servers using a valid username & password and get the same error every time.

InternetOpen succeeds, InternetConnect succeeds, FtpPutFile returns FALSE, GetLastError returns 12018.

The error message 12018 is defined in WinInet.h as follows
#define ERROR_INTERNET_INCORRECT_HANDLE_TYPE 12018
The type of handle supplied is incorrect for this operation.

Any input is greatly appreciated!

<br />
void CWinInetTestDlg::OnPut() <br />
{<br />
	DWORD err = 0;<br />
	CString str;<br />
<br />
	<br />
	HINTERNET hInternet = 0;<br />
<br />
<br />
	//	InternetOpen Params<br />
	LPCTSTR agent = _T("FTP");<br />
	DWORD dwAccessType = INTERNET_OPEN_TYPE_PRECONFIG;<br />
	LPCTSTR proxy = 0;<br />
	LPCTSTR bypass = 0;<br />
	DWORD flags = 0;<br />
<br />
<br />
	//	InternetConnect Params<br />
	LPCTSTR server = _T("X.X.X.X");<br />
	INTERNET_PORT port = INTERNET_DEFAULT_FTP_PORT;<br />
	LPCTSTR user = _T("user_name");<br />
	LPCTSTR pass = _T("password");<br />
	DWORD service = INTERNET_SERVICE_FTP;<br />
	DWORD context = 0;<br />
<br />
<br />
	//	FtpPutFile Params<br />
	LPCTSTR szLocalFile = _T("\\TEST.TXT");<br />
	LPCTSTR szRemoteFile = _T("\\TEST.TXT");<br />
<br />
<br />
<br />
	hInternet = InternetOpen(agent, dwAccessType, proxy, bypass, flags);<br />
	if (hInternet) {<br />
		<br />
		//flags = INTERNET_FLAG_PASSIVE;<br />
		flags = 0;<br />
		if (InternetConnect(<br />
			hInternet, <br />
			server, <br />
			port, <br />
			user, <br />
			pass, <br />
			service, <br />
			flags, <br />
			context)) {<br />
<br />
			flags = INTERNET_FLAG_TRANSFER_BINARY;<br />
			<br />
			if ( FtpPutFile(<br />
				hInternet, <br />
				szLocalFile, <br />
				szRemoteFile, <br />
				flags, <br />
				context) ) {<br />
				<br />
				MessageBox(<br />
					_T("FtpPutFile Success!"), <br />
					_T("WinInet FTP Test"),<br />
					MB_OK);<br />
<br />
			}else{<br />
				err = GetLastError();<br />
				str.Format(_T("FtpPutFile Error: %d"), err);<br />
				MessageBox(str, _T("WinInet FTP Test"),MB_OK);<br />
			}//FTPPutFile<br />
<br />
		}else{<br />
			err = GetLastError();<br />
			str.Format(_T("InternetConnect Error: %d"), err);<br />
			MessageBox(str, _T("WinInet FTP Test"),MB_OK);<br />
		}//InternetConnect<br />
<br />
		if (!InternetCloseHandle(hInternet)) {<br />
			err = GetLastError();<br />
			str.Format(_T("Error %d"), err);<br />
			MessageBox(str, _T("WinInet FTP Test"),MB_OK);<br />
		}//InternetCloseHandle<br />
<br />
	}else{<br />
		err = GetLastError();<br />
		str.Format(_T("InternetOpen Failed with code %d"), err);<br />
		MessageBox(str, _T("WinInet FTP Test"),MB_OK);<br />
	}//InternetOpen<br />
	<br />
}

-Ryan Bradley

Re: WinInet FtpPutFile

Michael Dunn17-Feb-06 15:53

Reading file with X/Y axes?

17-Feb-06 15:53

Two problems. 1) InternetConnect() return a HINTERNET but you're treating it like it returns a bool. 2) You're passing the wrong handle to FtpPutFile(), you need to pass it the handle returned by InternetConnect().

--Mike--
Visual C++ MVP Cool | :cool:

LINKS~! Ericahist | NEW!! PimpFish | CP SearchBar v3.0 | C++ Forum FAQ

Re: WinInet FtpPutFile

rbrad1234518-Feb-06 16:48

rbrad12345

18-Feb-06 16:48

Outstanding! Thank you!

Ryan Bradley
Systems Engineer
Industrial Networks

MFC42UD.lib

super17-Feb-06 13:56

super

17-Feb-06 13:56

Hi,
In release mode , the project is searching for MFC42UD.lib file.
Any idea why and where we have to chnge the project settings, because to my knowledge somebody tampered with the settings

cheers,
Super
------------------------------------------
Too much of good is bad,mix some evil in it

Re: MFC42UD.lib

super17-Feb-06 14:04

super

17-Feb-06 14:04

Dont worry.
I figured it myself.
Somebody has changed the release setting to debug settings.

cheers,
Super
------------------------------------------
Too much of good is bad,mix some evil in it

Lord Kixdemp17-Feb-06 13:20

Lord Kixdemp

17-Feb-06 13:20

Hello everyone! Big Grin | :-D

Am I reading my file correctly?

        for (int i = 0; i <= HEIGHT/32; i++)<br />
		{<br />
			char * curLine = new char[WIDTH/32];<br />
			f[x]->getline(curLine, WIDTH/32);<br />
<br />
			for (int j = 0; j <= WIDTH/32; j++)<br />
			{<br />
<br />
				// Get character in temp line<br />
				char v = curLine[j];<br />
<br />
				// Exit if EOF was found<br />
				if (!f[x]->good())<br />
					return;<br />
<br />
				if (x == 0)<br />
					fputc(v, outputz);

I noticed that if I open the file in Notepad, the character counter says 16, but if I count the chars with my fingers, I only get 15! Mad | :mad:

I want to get each line, and then write each character in that line to another file, individually. What's the right way of doing it? Much thanks! Wink | ;-)

PS: I've been struggling with this program for more than 1 month... I suck... Confused | :confused:

Lord Kixdemp
www.SulfurMidis.com
www.SulfurSoft.tk
[ftp://][http://][hotline://]tsfc.ath.cx

Re: Reading file with X/Y axes?

Lord Kixdemp17-Feb-06 15:40

Lord Kixdemp

17-Feb-06 15:40

Update!

I got the main problem away (NULL characters showing up at end of each line)
But now, the last line doesn't get written... Here's the updated code:

        for (int i = 0; i <= HEIGHT/32; i++)<br />
		{<br />
			char * curLine = new char[WIDTH/32];<br />
			f[x]->getline(curLine, WIDTH/32);<br />
<br />
			for (int j = 0; j < WIDTH/32-1; j++)<br />
			{<br />
<br />
				// Get character in temp line<br />
				char v = curLine[j];<br />
<br />
				// Exit if EOF was found<br />
				if (!f[x]->good())<br />
					return;<br />
<br />
				if (x == 0)<br />
					fputc(v, outputz);

Much thanks! Wink | ;-)

Lord Kixdemp
www.SulfurMidis.com
www.SulfurSoft.tk
[ftp://][http://][hotline://]tsfc.ath.cx

[registry] get all values in a key

Sam 200617-Feb-06 12:42

Sam 2006

17-Feb-06 12:42

hi,

i'm new to c++, still learning it. i am trying to learn some basic registry functions for use in other programs i may make. i have a subkey: currentuser/software/name/program

inside "program" i have a few values (all strings). how can i get the list of all values in the subkey?

i'm looking for the simplest possible way.RegCloseKey(hKey);
thanks in advance,
sam kline

-- modified at 18:46 Friday 17th February, 2006

Michael Dunn17-Feb-06 15:54

17-Feb-06 15:54

Look up RegEnumValue()

--Mike--
Visual C++ MVP Cool | :cool:

LINKS~! Ericahist | NEW!! PimpFish | CP SearchBar v3.0 | C++ Forum FAQ

Sam 200618-Feb-06 4:55

Sam 2006

18-Feb-06 4:55

ok, i've tried this code, but i cant figure out how to display 'cchValue'. any ideas?

thanks in advance,
sam kline

TCHAR    achKey[MAX_KEY_LENGTH];   // buffer for subkey name
    DWORD    cbName;                   // size of name string 
    TCHAR    achClass[MAX_PATH] = TEXT("");  // buffer for class name 
    DWORD    cchClassName = MAX_PATH;  // size of class string 
    DWORD    cSubKeys=0;               // number of subkeys 
    DWORD    cbMaxSubKey;              // longest subkey size 
    DWORD    cchMaxClass;              // longest class string 
    DWORD    cValues;              // number of values for key 
    DWORD    cchMaxValue;          // longest value name 
    DWORD    cbMaxValueData;       // longest value data 
    DWORD    cbSecurityDescriptor; // size of security descriptor 
    FILETIME ftLastWriteTime;      // last write time 
	HKEY hKey; 
    DWORD i, retCode; 
	char temp[9999];
    TCHAR  achValue[MAX_VALUE_NAME]; 
    DWORD cchValue = MAX_VALUE_NAME; 
 
	RegOpenKeyEx(HKEY_CURRENT_USER, TEXT("Software\\name\\something"), 0, KEY_QUERY_VALUE, &hKey);

    retCode = RegQueryInfoKey(
        hKey,                    // key handle 
        achClass,                // buffer for class name 
        &cchClassName,           // size of class string 
        NULL,                    // reserved 
        &cSubKeys,               // number of subkeys 
        &cbMaxSubKey,            // longest subkey size 
        &cchMaxClass,            // longest class string 
        &cValues,                // number of values for this key 
        &cchMaxValue,            // longest value name 
        &cbMaxValueData,         // longest value data 
        &cbSecurityDescriptor,   // security descriptor 
        &ftLastWriteTime);       // last write time 

	for (i=0, retCode=ERROR_SUCCESS; i<cValues; i++) 
    { 
        cchValue = MAX_VALUE_NAME; 
        achValue[0] = '\0'; 
        retCode = RegEnumValue(hKey, i, achValue, &cchValue, NULL, NULL, NULL, NULL);

        if (retCode == ERROR_SUCCESS ) 
		{			
			sprintf(temp, "%d: %s - ", i, achValue);
//i want 'cchValue' after the -, how can i do that?
			somelistbox.AddString(temp);
        } 
    }
	RegCloseKey(hKey);

-- modified at 10:55 Saturday 18th February, 2006

Ganesh_T18-Feb-06 1:40

Ganesh_T

18-Feb-06 1:40

You can use this function:
Here you have to pass the valueName to access it's value.
Specify the Root key where your subkey is located

CString YourClassName::GetValueFromRegistry(CString regValuName)
{
char lszValue[255];
CString str ;
HKEY hKey;
LONG returnStatus;
DWORD dwType=REG_SZ;
DWORD dwSize=255;
returnStatus = RegOpenKeyEx(HKEY_CURRENT_USER, "currentuser\\software\\name\\program", 0L, KEY_ALL_ACCESS, &hKey);
if (returnStatus == ERROR_SUCCESS)
{
returnStatus = RegQueryValueEx(hKey,regValuName, NULL, &dwType,(LPBYTE)&lszValue, &dwSize);
if(returnStatus == ERROR_SUCCESS)
{
str = (LPCTSTR)lszValue;
}
else
{
str="";
}
}
else
{
str="";
}
RegCloseKey(hKey);

return str;
}

Cheers
"Peace of mind through Technology"

How include extern DLL's as static Library into project?

Sam 200618-Feb-06 5:26

Sam 2006

18-Feb-06 5:26

oh, i just realized that that code worked!

thanks a lot!
sam kline

@LX17-Feb-06 12:42

@LX

17-Feb-06 12:42

Hi everybody,

I want to include few external DLL files into my executable file as a static Library.

Microsoft Visual C++ can do that with MFC,my question is: How can I do to insert external DLL's files?

I hope any body can help me!

Thanks

aLx

aLx

Re: How include extern DLL's as static Library into project?

John M. Drescher17-Feb-06 13:29

John M. Drescher

17-Feb-06 13:29

@LX wrote:
I want to include few external DLL files into my executable file as a static Library.

That is not possible.

John

Re: How include extern DLL's as static Library into project?

Michael Dunn17-Feb-06 15:55