Too few parameters in call to 'factorial(int,int)'

disk97 · #1 24-Mar-2009, 01:13

Hi, I got problem in my code.

could anyone help me this?

I think this is not that hard for someone but it's hard for me..

my purpose and code below;

<purpose>
The binomial coefficient is defined as n!/(k!(n-k)! when n and k are

nonnegative integers, and 0<=k<=n. If n<0,k<0 or k>n , the binomial

coefficient is considered to be zero. Also, n=0 and k=0 is considered to be 1.

CPP / C++ / C Code:

#include<iostream>
#include<iomanip>

using namespace std;

int factorial(int n,int k);

const double impossible=-9999;

void main()
{
	int n,k;
	cout<<"type in n: ";
	cin>>n;
	cout<<"type in k: ";
	cin>>k;
	char flag = 'y';
	while (flag=='y'||flag == 'Y')
	{
		cout<<"The binomial coefficient C("<<n<<','<<k<<")="<<factorial(n,k);
		cout<<'.'<<endl;
	}
	cout<< "Do you wish to compute another binomial coefficient?\n";
	cout<<"If so, enter 'y' or 'Y', otherwise type anything else.\n";
	cin>>flag;
}


int factorial(int n,int k)
{
	if (0<=k && k<=n)
		return n*factorial(n-1)/k*factorial(k-1)*(n-k)*factorial(n-k-1);
	else if (n<0 && k<0)
		return 0;
	else if (k>n)
		return 0;
	else if (n==0 && k==0)
		return 1;
	else
		return -9999;
}

thank you.

L7Sqr · #2 24-Mar-2009, 06:07

First you declare factorial to take two arguments as described below

Code:

int factorial(int n,int k);

Then you call it recursively with only a single argument

Code:

return n*factorial(n-1)/k*factorial(k-1)*(n-k)*factorial(n-k-1);

Realize that each of those recursive calls only has a single argument.
Either change your declaration (and definition) of factorial to be something like

Code:

int factorial(int x);

or provide the extra parameters to the function that exists now.

disk97 · #3 24-Mar-2009, 10:03

thank you for your answer.
I still have a question that I have to consider about two parameter such as n,k.

That's why I mentioned two parameters in the factorial function.

So, how can I handle two parameters in my code?

Do I have to declare another factorial fuction for k?

L7Sqr · #4 24-Mar-2009, 12:42

A function is non-changing; its definition is compiled to a concrete set of instructions that will always execute the same way given the same parameters. If you wish to have separate behaviors, then you must create separate functions.
For example:

CPP / C++ / C Code:

int foo1(int arg1) {
   int i = 0;
   for (; i < arg1; ++i) {
      printf ("i : %d\n", i);
   }
   return i;
}

Will not do the same thing as

CPP / C++ / C Code:

int foo2 (int arg1, int arg2) {
   int i = 0;
   for (; i < arg1; i += arg2) {
      printf ("i : %d\n", i);
   }
   return i;
}

Nor can you call them the same way

CPP / C++ / C Code:

foo1 (100); /* Ok */
foo1 (100, 10); /* Error, wrong number of arguments */
foo2 (100); /* Error wrong number of arguments */
foo2 (100, 10); /* Ok */

Kimmo · #5 25-Mar-2009, 13:29

I'd just like to point out that your factorial function doesn't actually calculate any factorials, as one would assume from it's name. You would also do well to think about what actually is happening in your recursive calls.

This is what happens (I'll just assume small numbers of n = 3, k = 1. Guess we also have to assume you pass k as the second argument):

Code:

3 * factorial(3 - 1, 1)
  if (0<=k && k<=n) // true, n = 2, k = 1
    2 * factorial(2 - 1, 1)
    if (0<=k && k<=n) // true, n = 1, k = 1
      1 * factorial(1 - 1, 1)
      else if (k > n) // true, n = 0, k = 1
        return 0;

We got a 0. Multiplying 0 by anything yields 0. Dividing 0 by anything yields 0. In fact, from this follows that your program would always tell the answer is 0. Except when k = 0 and k >= n, in which case it crashes because of division by zero error.

The solution is simple: Create a factorial function that actually calculates the factorial and nothing else. Then you can write simply

CPP / C++ / C Code:

factorial(n) / factorial(k) * factorial(n - k);

Your while loop is also infinite, since flag never changes inside it.

disk97 · #6 25-Mar-2009, 21:13

Thank you very much L7sqr and Kimmo!

I got all of my problems!

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Too few parameters in call to 'factorial(int,int)'

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