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Jul 19th, 2004

factorial using a for loop

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I need to write a program which will execute a factorial, but with an upper and lower bound. Here's what I've written, but it's not working. I keep getting an error message on the for command with expression syntax. Please, I've got to have this and much much more by wednesday.

Thanks!

C++ Syntax (Toggle Plain Text)
#include <iostream.h>
 
 
#define q = 3
 
int main()
 
 
{
   int n;
	if  (n < 0) return 0;
   int f;
 
   for (n=1; n <= q; n++)
   {
      double f = 1;
   	{f *= n;}
    }
 
   cout<< f;
   char w;
   cin>>w;
   return 0;
}
#include <iostream.h>


#define q = 3

int main()


{
   int n;
	if  (n < 0) return 0;
   int f;

   for (n=1; n <= q; n++)
   {
      double f = 1;
   	{f *= n;}
    }

   cout<< f;
   char w;
   cin>>w;
   return 0;
}

Last edited by Nick Evan; Jan 27th, 2010 at 11:03 am. Reason: Added code-tags

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ellisrn

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Jul 19th, 2004

Re: factorial using a for loop

The following header is deprected, instead try to use <iostream>

C++ Syntax (Toggle Plain Text)

#include <iostream.h>

You shouldn't have the equals sign here.

C++ Syntax (Toggle Plain Text)

#define q = 3

I have no idea what this is intended to do.

C++ Syntax (Toggle Plain Text)
int n;
if (n < 0) return 0;
int n;
if (n < 0) return 0;

Again, your code it a little unclear here. It says to declare a variable f, set it equal to 1 and then multiply by n. This f and the int f previously declared are different.

C++ Syntax (Toggle Plain Text)
for (n=1; n <= q; n++)
{
double f = 1;
{f *= n;}
}
for (n=1; n <= q; n++)
{
double f = 1;
{f *= n;}
}

When the loop finishes, the double f should go out of scope. So the value that is being printed at the end is the uninitialized value of the int f.

(If it were to compile.)

It couldn't hurt to use more descriptive names, too. Maybe something like this.

C++ Syntax (Toggle Plain Text)
#include <iostream> // let's try to use a compiler from this millenium
 
int main()
{
int n, result = 1, value = 3;
for ( n = 1; n <= value; n++ )
{
	 result *= n;
}
std::cout << value << "! = " << result << std::endl;
std::cin.get(); // pause ???
return 0;
}
 
/* my output
3! = 6
*/
#include <iostream> // let's try to use a compiler from this millenium
 
int main()
{
int n, result = 1, value = 3;
for ( n = 1; n <= value; n++ )
{
	 result *= n;
}
std::cout << value << "! = " << result << std::endl;
std::cin.get(); // pause ???
return 0;
}
 
/* my output
3! = 6
*/

Dave Sinkula

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Jul 19th, 2004

Re: factorial using a for loop

Thanks, I'll try and integrate this into my monster program.

Quote originally posted by Dave Sinkula ...

The following header is deprected, instead try to use <iostream>
C++ Syntax (Toggle Plain Text)
#include <iostream.h>
#include <iostream.h>
You shouldn't have the equals sign here.
C++ Syntax (Toggle Plain Text)
#define q = 3
#define q = 3
I have no idea what this is intended to do.
C++ Syntax (Toggle Plain Text)
int n;
if (n < 0) return 0;
int n; if (n < 0) return 0;
Again, your code it a little unclear here. It says to declare a variable f, set it equal to 1 and then multiply by n. This f and the int f previously declared are different.
C++ Syntax (Toggle Plain Text)
for (n=1; n <= q; n++)
{
double f = 1;
{f *= n;}
}
for (n=1; n <= q; n++) { double f = 1; {f *= n;} }
When the loop finishes, the double f should go out of scope. So the value that is being printed at the end is the uninitialized value of the int f.

(If it were to compile.)

It couldn't hurt to use more descriptive names, too. Maybe something like this.
C++ Syntax (Toggle Plain Text)
#include <iostream> // let's try to use a compiler from this millenium
 
int main()
{
int n, result = 1, value = 3;
for ( n = 1; n <= value; n++ )
{
	 result *= n;
}
std::cout << value << "! = " << result << std::endl;
std::cin.get(); // pause ???
return 0;
}
 
/* my output
3! = 6
*/
#include <iostream> // let's try to use a compiler from this millenium int main() { int n, result = 1, value = 3; for ( n = 1; n <= value; n++ ) { result *= n; } std::cout << value << "! = " << result << std::endl; std::cin.get(); // pause ??? return 0; } /* my output 3! = 6 */

ellisrn

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Jul 20th, 2004

Re: factorial using a for loop

see this example dude

C++ Syntax (Toggle Plain Text)
int main()
{
int num;
do{
cout << "Enter a number between 1 and 10";
cin>>num;
}while( num < 1 || num > 10 ); /* ask some more if we dont get something between 1 and 10 */
double factorial( num );
for( int n(num-1) ; n > 0 ; factorial *= n, --n); /* demonstration of how the for loop can be extremely useful */
cout << "The factorial of "<< num << " is "<< factorial << endl;
}
int main()
{
int num;
do{
cout << "Enter a number between 1 and 10";
cin>>num;
}while( num < 1 || num > 10 ); /* ask some more if we dont get something between 1 and 10 */
double factorial( num );
for( int n(num-1) ; n > 0 ; factorial *= n, --n); /* demonstration of how the for loop can be extremely useful */
cout << "The factorial of "<< num << " is "<< factorial << endl;
}

meabed

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Jul 20th, 2004

-1

Re: factorial using a for loop

Hi Guys
actually it is the first time to write to you
i have only 3 quistions and if any one of you has the answer for it please give it to me cause i need it very very urgent:

the first quistion is for factorial also but in PASCAL :
i want to have a program written in PASCAL that calculate the factorial ..but this program must contain stacks..i gave up looking fo the answer cause i didnt found it

so pleaaase heeeelp meee.

the second quistion is in PASCAL also :
i want to write a program in PASCAL using arrays that can recieve marks of 10 students in 5 subjects then calculate :
1- the average of every student
2 - the average of every subject
3 - the general average of all subjects an all students
4 - the highest mark & the lowest mark.

the third one is in C++ .. i need a programe for three hotdog shops
that recieve how many hotdog and how many bread in each shop then recordin every sale process by losing 1 bread & 1 hot dog every time
and i can ask at any place in programm about the amount of hotdog and bread in each shop
also it must contain a summary at the end of the day about how many bread & hot dog at the end of the day.

well .. i know it is too defficult but please i want it urgent as soon as posiple
please send it to my email at
<<snip>>

Last edited by Nick Evan; Jan 27th, 2010 at 11:04 am. Reason: removed mail

ahsn

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Jul 20th, 2004

-2

Re: factorial using a for loop

i can help u with the first .. cuz really i'm not expert with pascal but i know little about it .

.. see this code this what i learned in pascal

C++ Syntax (Toggle Plain Text)
{---------------------------------------------------------------------
 PROGRAM: FACTORIAL2.PAS
 Version:				   Turbo Pascal 6.0
 -------------------------------------------------------------------}
PROGRAM Factrl2 (Input, Output);
USES
  Crt;
CONST
  MaxM  =  7;
VAR
  Choice,
  M			:  Integer;
  UserQuits	:  BOOLEAN;
{------------------------------------}
{			PROCEDURES			  }
{------------------------------------}
{-----------------------------}
{		  INIT.PROC		  }
{-----------------------------}
PROCEDURE Init;
BEGIN
  TextBackground(Blue);				   { Sets colors					 }
  TextColor(White);
  Window(0,0,80,25);
  ClrScr;
END;
 
{-----------------------------}
{		 .PROC		   }
{-----------------------------}
PROCEDURE Null;
BEGIN
END;
{-----------------------------}
{	  FACTFORDO .PROC		}
{-----------------------------}
PROCEDURE FactForDo;
VAR
  k,								   { index }
  FAC,
  Factorial		 :  INTEGER;		{ partial factorial }
BEGIN
  ClrScr;
  WriteLn;
  Write(' ':20,' Enter an integer - 0 to ',MaxM,': ');
  ReadLn(M);
  IF M <= MaxM THEN
	BEGIN
	  FAC := 1;
	  FOR k := 2 to M DO
		FAC := FAC * K;
	  Factorial := FAC;
	  WriteLn;
	  WriteLn(' ':20,'		  M was entered as: ', M );
	  WriteLn;
	  WriteLn(' ':20,'	   M!, or M Factorial = ', Factorial );
	END
	ELSE
	  BEGIN
		WriteLn;
		WriteLn('The number you entered is greater than ',MaxM,'.  Re-enter. ');
	  END;  { ELSE }
  WriteLn;
  WriteLn(' Press <ENTER> to return to menu.');
  ReadLn;
END;	  {FactForDo}
 
{-----------------------------}
{	  FACTORIAL.PROC		 }
{-----------------------------}
FUNCTION Factorial ( M : Integer ) : Integer;
BEGIN
  IF M = 0 THEN
	Factorial := 1
  ELSE
	Factorial := M * Factorial( M-1 );
END;	  { Factorial }
 
{-----------------------------}
{		FACTREC.PROC		 }
{-----------------------------}
PROCEDURE FactRec;
BEGIN
  ClrScr;
  WriteLn;
  Write(' ':20,'Enter an integer - 0 to ',MaxM,': ');
  ReadLn(M);
  WriteLn;
  IF M > MaxM THEN
	WriteLn('The number you entered is greater than ',MaxM,'.  Re-enter. ')
	ELSE
	  BEGIN
		WriteLn;
		WriteLn(' ':20,'		  M was entered as: ', M );
		M := Factorial( M );
	  END;  { ELSE }
  WriteLn;
  WriteLn(' ':20,'	   M!, or M Factorial = ', M );
  WriteLn;
  WriteLn(' Press <ENTER> to return to menu.');
  ReadLn;
END;	  {FactRec}
 
{------------------------------------}
{		   MAIN PROGRAM			 }
{------------------------------------}
BEGIN
  Init;
  UserQuits := False;
  REPEAT
	ClrScr;
	WriteLn;
	WriteLn(' ':25, ' Menu For Factorial Methods ' );
	WriteLn;
	WriteLn(' ':20, ' 1.  Factorial Using a FOR DO Loop' );
	WriteLn(' ':20, ' 2.  Factorial Using Recursion'	 );
	WriteLn(' ':20, ' 3.  Quit '						 );
	ReadLn ( Choice );
	CASE Choice OF
	   1  :  FactForDo;
	   2  :  FactRec;
	   3  :  UserQuits := True;
	END;
  UNTIL UserQuits;
END.
{---------------------------------------------------------------------
 PROGRAM: FACTORIAL2.PAS
 Version:				   Turbo Pascal 6.0
 -------------------------------------------------------------------}
PROGRAM Factrl2 (Input, Output);
USES
  Crt;
CONST
  MaxM  =  7;
VAR
  Choice,
  M			:  Integer;
  UserQuits	:  BOOLEAN;
{------------------------------------}
{			PROCEDURES			  }
{------------------------------------}
{-----------------------------}
{		  INIT.PROC		  }
{-----------------------------}
PROCEDURE Init;
BEGIN
  TextBackground(Blue);				   { Sets colors					 }
  TextColor(White);
  Window(0,0,80,25);
  ClrScr;
END;
 
{-----------------------------}
{		 .PROC		   }
{-----------------------------}
PROCEDURE Null;
BEGIN
END;
{-----------------------------}
{	  FACTFORDO .PROC		}
{-----------------------------}
PROCEDURE FactForDo;
VAR
  k,								   { index }
  FAC,
  Factorial		 :  INTEGER;		{ partial factorial }
BEGIN
  ClrScr;
  WriteLn;
  Write(' ':20,' Enter an integer - 0 to ',MaxM,': ');
  ReadLn(M);
  IF M <= MaxM THEN
	BEGIN
	  FAC := 1;
	  FOR k := 2 to M DO
		FAC := FAC * K;
	  Factorial := FAC;
	  WriteLn;
	  WriteLn(' ':20,'		  M was entered as: ', M );
	  WriteLn;
	  WriteLn(' ':20,'	   M!, or M Factorial = ', Factorial );
	END
	ELSE
	  BEGIN
		WriteLn;
		WriteLn('The number you entered is greater than ',MaxM,'.  Re-enter. ');
	  END;  { ELSE }
  WriteLn;
  WriteLn(' Press <ENTER> to return to menu.');
  ReadLn;
END;	  {FactForDo}
 
{-----------------------------}
{	  FACTORIAL.PROC		 }
{-----------------------------}
FUNCTION Factorial ( M : Integer ) : Integer;
BEGIN
  IF M = 0 THEN
	Factorial := 1
  ELSE
	Factorial := M * Factorial( M-1 );
END;	  { Factorial }

{-----------------------------}
{		FACTREC.PROC		 }
{-----------------------------}
PROCEDURE FactRec;
BEGIN
  ClrScr;
  WriteLn;
  Write(' ':20,'Enter an integer - 0 to ',MaxM,': ');
  ReadLn(M);
  WriteLn;
  IF M > MaxM THEN
	WriteLn('The number you entered is greater than ',MaxM,'.  Re-enter. ')
	ELSE
	  BEGIN
		WriteLn;
		WriteLn(' ':20,'		  M was entered as: ', M );
		M := Factorial( M );
	  END;  { ELSE }
  WriteLn;
  WriteLn(' ':20,'	   M!, or M Factorial = ', M );
  WriteLn;
  WriteLn(' Press <ENTER> to return to menu.');
  ReadLn;
END;	  {FactRec}
 
{------------------------------------}
{		   MAIN PROGRAM			 }
{------------------------------------}
BEGIN
  Init;
  UserQuits := False;
  REPEAT
	ClrScr;
	WriteLn;
	WriteLn(' ':25, ' Menu For Factorial Methods ' );
	WriteLn;
	WriteLn(' ':20, ' 1.  Factorial Using a FOR DO Loop' );
	WriteLn(' ':20, ' 2.  Factorial Using Recursion'	 );
	WriteLn(' ':20, ' 3.  Quit '						 );
	ReadLn ( Choice );
	CASE Choice OF
	   1  :  FactForDo;
	   2  :  FactRec;
	   3  :  UserQuits := True;
	END;
  UNTIL UserQuits;
END.

meabed

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Mar 30th, 2009

-1

veeeeeeery Urgent

Hi Guys>>
It is first time to write 4 u but actually I have one eq only >> so if u can help>>it is also about the factorial by using loop>>
the Q is

The value of Euler's number e,can be approximates using this formula
e=1+1/1!+1/2!+1/3!+1/4!........
using this formula,write a c++ program that approximates the value of e using a while loop that terminates when the difference between two successive approximates differ by less than 10^-9.

Thanx any way

still student

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Jan 27th, 2010

-2

what about 100! ?

Click to Expand / Collapse Quote originally posted by Dave Sinkula ...

The following header is deprected, instead try to use <iostream>
C++ Syntax (Toggle Plain Text)
#include <iostream.h>
#include <iostream.h>
You shouldn't have the equals sign here.
C++ Syntax (Toggle Plain Text)
#define q = 3
#define q = 3
I have no idea what this is intended to do.
C++ Syntax (Toggle Plain Text)
int n;
if (n < 0) return 0;
int n; if (n < 0) return 0;
Again, your code it a little unclear here. It says to declare a variable f, set it equal to 1 and then multiply by n. This f and the int f previously declared are different.
C++ Syntax (Toggle Plain Text)
for (n=1; n <= q; n++)
{
double f = 1;
{f *= n;}
}
for (n=1; n <= q; n++) { double f = 1; {f *= n;} }
When the loop finishes, the double f should go out of scope. So the value that is being printed at the end is the uninitialized value of the int f.

(If it were to compile.)

It couldn't hurt to use more descriptive names, too. Maybe something like this.
C++ Syntax (Toggle Plain Text)
#include <iostream> // let's try to use a compiler from this millenium
 
int main()
{
int n, result = 1, value = 3;
for ( n = 1; n <= value; n++ )
{
	 result *= n;
}
std::cout << value << "! = " << result << std::endl;
std::cin.get(); // pause ???
return 0;
}
 
/* my output
3! = 6
*/
#include <iostream> // let's try to use a compiler from this millenium int main() { int n, result = 1, value = 3; for ( n = 1; n <= value; n++ ) { result *= n; } std::cout << value << "! = " << result << std::endl; std::cin.get(); // pause ??? return 0; } /* my output 3! = 6 */

i had it and founds that it just worked for small integer. when i try to generate 100! it turns out zero. how to solve the problem?

angieng

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Jan 27th, 2010

Re: factorial using a for loop

You cant use int for such big numbers as 100!, since int usually can handle 32bit value.
solution is google: "c++ big integer"

pecet

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Jan 27th, 2010

Re: factorial using a for loop

Click to Expand / Collapse Quote originally posted by ellisrn ...

I need to write a program which will execute a factorial, but with an upper and lower bound. Here's what I've written, but it's not working. I keep getting an error message on the for command with expression syntax. Please, I've got to have this and much much more by wednesday.

Thanks!

#include <iostream.h>

#define q = 3

int main()

{
int n;
if (n < 0) return 0;
int f;

for (n=1; n <= q; n++)
{
double f = 1;
{f *= n;}
}

cout<< f;
char w;
cin>>w;
return 0;
}

----------------------------------------------------------------------------------------
Try using array for your data set. For instance:
i

C++ Syntax (Toggle Plain Text)
nt numbers[50];//setup array
numbers[0]=1; //factorial of 0 is 1
int factorial = 0;//initialize your factorial
 
//loop will multiply all the numbers in the array
for (int i = 1; i < 50; i ++){
    factorial = numbers[i] * numbers[i -1];
 
}
 
cout <<"\nFactorial is: "<< factorial << endl;
nt numbers[50];//setup array
numbers[0]=1; //factorial of 0 is 1
int factorial = 0;//initialize your factorial

//loop will multiply all the numbers in the array
for (int i = 1; i < 50; i ++){
    factorial = numbers[i] * numbers[i -1];

}

cout <<"\nFactorial is: "<< factorial << endl;

##############---------
Don't forget to load array with the data set - where you can use another for loop to make achieve that, you can take as input lower and upper bound and set them in array as numbers[lower], numbers[upper], and you should have your program - keep in mind arrays[50] starts as array[0] and finishes as array[49];

Cheers.

Last edited by Nick Evan; Jan 27th, 2010 at 11:02 am. Reason: Added code-tags

akvino

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