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Should compute the following menu with call by reference. Thx for ur help.(ps : I'm not that gd in function)

cooka (5)
#include <iostream>
using namespace std;
void readValues (int & ,int &); // 2 values A and B
int factorial (int &); // A
int divCount (int); // A
void evSum (int &, int &,long); // A and B and I should have the long sum

int main ()
{
int A,B; int choice;

do {
cout<<"Enter a positive integer A :"<<endl; // how do I use call by reference to ask the user for A and B?
cin>>A;
cout<<"Enter a positive integer B :"<<endl;
cin>>B;
}while (A<=0 || B<=0 || A>B);

do {
cout<<"Choose a computation from the following menu :"
<<"1- Compute sum of the Factorials of "<<A<<"."
<<"2- Count all divisors of "<<A<<"."
<<"3- Compute the sum of all even integers between "<<A<<" and "<<B<<"."
<<"4- Exit the program.";
cin>>choice;

switch (choice) {

case 1 : {
cout<<"The following program computes the sum of factorials of "<<A<<"."<<endl;
long int sumFactorial = 0; //I want to compute 1! + 2! + 3! .....A! should I put this in main or not?
for (int K=1; K<=A;K++);
sumFactorial += factorial (A); // error saying that overloaded
cout<<"The sum of factorials of "<<A<<" is equal to :"<<sumFactorial<<endl;
break; }

case 2 : {
cout<<"The following program counts all the divisors of "<<A<<"."<<endl;
int divcount;
divcount = divCount (A); // It should count all divisors of A just count them and output the number
cout<<"The number of divisors of "<<A<<" is equal to : "<<divcount<<endl;
break; }

case 3 : {
cout<<"The following program computes sum of even integers between "<<A<<" and "<<B<<"."<<endl;
long int evsum = 0; // it should count the even integers between A and B.
evSum (A,B,evsum);
cout<<"The sum of even integers between "<<A<<" and "<<B<<" is equal to :"<<endl;
break; }

case 4 : {
cout<<"Exit the program"<<endl;
break; }
default :
cout<<"Wrong imput , Please choose a number from the menu."<<endl;
}
return 0;
}while (choice != 4);
}

long int factorial (int a) { // I need to use call by reference in these function to call the values

if(a == 0)
return 1; // I have some error that I can't understand . it's not working
else
return (a) * factorial(a - 1);

int divCount (int a) { // error on this brace

for (int i=1;i<=a;i++)
if (a % i == 0)
divCount++; // same in here I should call the values . I have error on "divCount" saying local function definitions are illegal.
return divCount;

void evSum (int a,int b) {

for ( int i>=a,i<=b,i++)
if (i % 2 == 0)
int evSum = 0; // I don't know if I should use "evsum" from main or "evSum"
evSum += i;
return evSum;
}
TarikNeaj (2580)
Hey. First of all, please edit your post and use code tags so it's readable - http://www.cplusplus.com/articles/jEywvCM9/

Second, all you did was give us your code. You didnt ask a question. What specifically do you need help with? Be specific.
cooka (5)
Sorry but I'm not familiar with tagging that y I couldn't do it. I have some prob with my functions . I still didn't understand how should I call them from main to compute and return them back. I should also use call by reference which I recently learnt I'm practicing on it but still struggling a bit plz read the messg (//....) I wrote if it helps. thx for ur help.
Last edited on
cooka (5)
I'm sorry I never used a forum before and I will try to help u as much as I can .
JLBorges (13770)
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#include <iostream>

// invariant: n! is within the range of unsigned int
unsigned int factorial( unsigned int n )
{ return n < 2 ? 1 : n * factorial(n-1) ; }

void factorial_byref( unsigned int n, unsigned int& result ) { result = factorial(n) ; }

// invariant: n != 0
unsigned int div_count( unsigned int n )
{
    if( n == 1 ) return 1 ;

    unsigned int cnt = 2 ; // 1 and n are divisors
    for( unsigned int div = 2 ; div <= (n/2) ; ++div ) if( n%div == 0 ) ++cnt ;
    return cnt ;
}

void div_count_byref( unsigned int n, unsigned int& result ) { result = div_count(n) ; }

// invariant: a <= b , sum is within the range of unsigned int
unsigned int ev_sum( unsigned int a, unsigned int b )
{
    if( a%2 != 0 ) return ev_sum( a+1, b ) ;

    // invariant: here, a is an even number
    unsigned int sum = 0 ;
    for( ; a <= b ; a += 2 ) sum += a ;
    return sum ;
}

void ev_sum_byref( unsigned int a, unsigned int b, unsigned int& result ) { result = ev_sum(a,b) ; }

int main()
{
    unsigned int n = 8 ;
    std::cout << "factorial(" << n << ") == " << factorial(n) << '\n' ;

    unsigned int fact ;
    factorial_byref( n, fact ) ;
    std::cout << "fact == " << fact << '\n' ;

    ///////////////////////////////////////////////////

    n = 100 ; // divisors are 1, 2, 4, 5, 10, 20, 25, 50, 100
    std::cout << "div_count(" << n << ") == " << div_count(n) << '\n' ;

    unsigned int dcnt ;
    div_count_byref( n, dcnt ) ;
    std::cout << "dcnt == " << dcnt << '\n' ;

    ///////////////////////////////////////////////////


    unsigned int a = 23 ;
    unsigned int b = 23 ;
    std::cout << "ev_sum( " << a << ", " << b << " ) == " << ev_sum(a,b) << '\n' ;

    b = 24 ;
    std::cout << "ev_sum( " << a << ", " << b << " ) == " << ev_sum(a,b) << '\n' ;

    a = 1 ;
    b = 201 ;
    std::cout << "ev_sum( " << a << ", " << b << " ) == " << ev_sum(a,b) << '\n' ;
    // 2 + 4 + ... + 200 == 2 * ( 1 + 2 + ... + 100 ) == 2 * 100 * 101 / 2 == 100 * 101 == 10100

    unsigned int sum ;
    ev_sum_byref( a, b, sum ) ;
    std::cout << "sum == " << sum << '\n' ;
}

http://coliru.stacked-crooked.com/a/53f327ca9aecf0ff
eec (26)
first you can use online Code formatter to beautify code.
http://www.tutorialspoint.com/online_c_formatter.htm

and for using code tag simpley select < > icon in right panel in Foramt: section and simply
put your code in enclosing tag

finaly your beautified code is here:


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#include <iostream>
using namespace std;
void readValues (int & ,int &); // 2 values A and B
int factorial (int &); // A
int divCount (int); // A
void evSum (int &, int &,long); // A and B and I should have the long sum

int main ()
{
    int A,B;
    int choice;

    do {
        cout<<"Enter a positive integer A :"<<endl; 
        // how do I use call by reference to ask the user for A and B?
        cin>>A;
        cout<<"Enter a positive integer B :"<<endl;
        cin>>B;
    } while (A<=0 || B<=0 || A>B);

    do {
        cout<<"Choose a computation from the following menu :"
            <<"1- Compute sum of the Factorials of "<<A<<"."
            <<"2- Count all divisors of "<<A<<"."
            <<"3- Compute the sum of all even integers between "<<A<<" and "
            <<B<<"."
            <<"4- Exit the program.";
        cin>>choice;

        switch (choice) {

        case 1 : {
            cout<<"The following program computes the sum of factorials of "
            <<A<<"."<<endl;
            long int sumFactorial = 0; //I want to compute 1! + 2! + 3! .....
            //A! should I put this in main or not?
            for (int K=1; K<=A; K++);
            sumFactorial += factorial (A); // error saying that overloaded
            cout<<"The sum of factorials of "<<A<<" is equal to :"<<sumFactorial
            <<endl;
            break;
        }

        case 2 : {
            cout<<"The following program counts all the divisors of "<<A<<"."
            <<endl;
            int divcount;
            divcount = divCount (A); // It should count all divisors of A just 
            //count them and output the number
            cout<<"The number of divisors of "<<A<<" is equal to : "
            <<divcount<<endl;
            break;
        }

        case 3 : {
            cout<<"The following program computes sum of even integers between "
            <<A<<" and "<<B<<"."<<endl;
            long int evsum = 0; // it should count the even integers between A 
            //and B.
            evSum (A,B,evsum);
            cout<<"The sum of even integers between "<<A<<" and "<<B<<" is equal
            // to :"<<endl;
            break;
        }

        case 4 : {
            cout<<"Exit the program"<<endl;
            break;
        }
        default :
            cout<<"Wrong imput , Please choose a number from the menu."<<endl;
        }
        return 0;
    } while (choice != 4);
}

long int factorial (int a) { // I need to use call by reference in these 
	//function to call the values

    if(a == 0)
        return 1; // I have some error that I can't understand . it's not working
    else
        return (a) * factorial(a - 1);

    int divCount (int a) { // error on this brace

        for (int i=1; i<=a; i++)
            if (a % i == 0)
                divCount++; // same in here I should call the values . 
     //I have error on "divCount" saying local function definitions are illegal.
        return divCount;

        void evSum (int a,int b) {

            for ( int i>=a,i<=b,i++)
                if (i % 2 == 0)
                    int evSum = 0; // I don't know if I should use "evsum" from
                    // main or "evSum"
            evSum += i;
            return evSum;
        }


reading http://www.cplusplus.com/articles/jEywvCM9/
must clearify all unclear aspect of using forum.
Last edited on
eec (26)
hi cooka, seems you are a student and this is a college program.
as i see many simple programming errors in your code i will suggest to you these steps:

1. try to find a talent classmate to study computer programs together not alone.
2. listen to your professor advices.
3. read all tutorial in http://www.cplusplus.com/doc/tutorial/
3. Work Work Work Hard to find and implement code by own

finally your corrected code is here

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#include <iostream>
using namespace std;



/// i highly recomment to not use this function declaration as begineer
//~ void readValues (int & ,int &); // 2 values A and B
//~ long int factorial (int ); // A
//~ int divCount (int); // A
//~ void evSum (int &, int &,long int ); // A and B and I should have the 
//long sum


void
evSum (int &a,int &b, long int &c) /// give 3 argument by ref, 
{
	///as c is by ref, calculated evSum assign to c 
	/// c hold it back, not return but hold it as i use call by reference
	
	long int  evSum=0;
	for ( int i=a+1;i<b;i++){
		if (i % 2 == 0){
			evSum += i;
			///cout<<evSum<<" "<<i<<endl; 
		}
	}

/// this last assign lead to c hold true value of evSum by ref
c = evSum;


///cout <<c;
}


///must use call by value as you have factorial(a-1) in orginal code but 
///this method correct it

/// get a by ref and compute factorial (a) and return it.
long int 
factorial (int &a)//
{ 
	int t=a;
	int s = t-1;
	
    if(t == 0)
        return 1; // I have some error that I can't understand . it's not 
        //working
    else
        return (t) * factorial(s);
}


int 
divCount (int &a) ///input a call by ref, return number of divisers 
{
	int divCount=0;
	for (int i=1; i<=a; i++){
		if (a % i == 0){
			divCount++;
		}
	}         
	
	return divCount;
}


/// he want to use call by reference to save memory 
int
main (int argc, char **argv)
{
    int A,B;
    int choice;

    do {
        cout<<"Enter a positive integer A :"; 
        // how do I use call by reference to ask the user for A and B?
        cin>>A;
        cout<<"Enter a positive integer B :";
        cin>>B;
    } while (A<=0 || B<=0 || A>B);//why A>B


    do {
        cout<<"Choose a computation from the following menu :"<<endl
            <<"1- Compute sum of the Factorials of "<<A<<"."<<endl
            <<"2- Count all divisors of "<<A<<endl
            <<"3- Compute the sum of all even integers between "<<A<<" and "
            <<B<<endl
            <<"4- Exit the program."<<endl;
        cin>>choice;

        switch (choice) {

        case 1 : {
            cout<<"The following program computes the sum of factorials of "
            <<A<<endl;
            long int sumFactorial = 0;
            //I want to compute 1! + 2! + 3! .....
            //A! should I put this in main or not?
            
            for (int K=1; K<=A; K++){
				sumFactorial += factorial (K); 
				// error saying that overloaded
            }
            
            cout<<"The sum of factorials of "<<A<<" is equal to :"
            <<sumFactorial
            <<endl;
            break;
        }

        case 2 : {
            cout<<"The following program counts all the divisors of "<<A
            <<endl;
            int divcount;
            divcount = divCount (A); // It should count all divisors of A just 
            //count them and output the number
            cout<<"The number of divisors of "<<A<<" is equal to : "
            <<divcount<<endl;
            break;
        }

        case 3 : {
            cout<<"The following program computes sum of even integers between"
            <<A<<" and "<<B<<"."<<endl;
            long int evsum = 0; // it should count the even integers between A 
            //and B.
            
            evSum (A,B,evsum);
            cout<<"The sum of even integers between "<<A<<" and "<<B<<
            " is equal to :"<<evsum<<endl;
            break;
        }

        case 4 : {
            cout<<"Exit the program"<<endl;
            break;
        }
        default :
            cout<<"Wrong imput , Please choose a number from the menu."<<endl;
        }
        return 0;
    } while (choice != 4);
}


to find how to use call by value/ reference read this link:

http://www.cplusplus.com/doc/tutorial/functions/

feel free to any other questions.


Last edited on
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