As you can see I am new here. I found this site from googling a question about a getChoice() function , and I was able to learn how to implement the function in my project to fit my needs from the post.
(http://www.daniweb.com/forums/thread162456.html). Well anyways, I have more issues that are giving me real big headaches and I wonder if you can give me a little guidance/aid:

I believe I have the menu set up to how I need it, and I also believe that the "Enter polynomial" part (Case 1) is correct. What I am confused about is Case 2 and 3. I haven't started/don't know where to start with Case 3 (integrating then evaluating from inputted limits [a,b]). Some guidance on where to go with that would be awesome.

Edit: case 3 is all good except if the coefficient is 1. I don't want the program to print a 1 in front of the x.
NOTE: I would like to use the prototypes listed at the bottom of the code, I have included more info within the code.

#include<iostream>
#include<cmath>
using namespace std;

int getChoice();
int firstChoice();
int getN();
double f(double x, double coef[], int n);
double integral(double a, double b, double coef[], int n);
void print_polynomial(double coef[], int n);


int main (void) {
    int userChoice;
    int n;
    int i;
    double polynom,a,b;
    double coef[10];
    cout << "This program finds definite integral\nof polynomial on [a,b]\n\n";
    cout << "0. Quit\n1. Enter Polynomial\n2. Print Polynomial\n3. Integrate\n\nEnter your choice: ";
    userChoice = firstChoice();
 do{
    switch(userChoice)
    {
    case 0: //ends program
            return 0;

    case 1:
            cout << "Enter degree of a polynom between 2 and 10 : ";
            n=getN();
            cout << "Enter space separated coefficients starting from highest degree\n";
            for(i=n;i>=0;i--)
                  cin>>coef[i];
            //prompts the user for the degree of the polynomial.
            //Degrees may not be less than 2 or greater than 10
            //for the purposes of this program. Continue prompting
            //the user for the degree until he inputs a valid one.
            //End result should be stored polynomial.
            break;

    case 2:  print_polynomial(coef,n);
            
            //prints the polynomial in standard form (highest degree first.)
            //I want to be able to get rid of the "1" in 1*x (aka if coefficient is 1, don't print 1.)
            break;

    case 3: //prompts the user for the integration limits a and b
            //then outputs the integral of the polynomial from a to b.
            cout<<"Enter the integration limits:\n";
            cin>>a>>b;
            integral(a,b,coef,n);
            break;
    }
    cout << "0. Quit\n1. Enter Polynomial\n2. Print Polynomial\n3. Integrate\n\nEnter your choice: ";
    userChoice=getChoice();
    }while(true);
  }



//Prototypes

//This prototype is built so the value 2 or 3 cannot be chose before a polynomial is inputted
//This only works the very first run of the program
int firstChoice()
{
    int choice;

    cin >> choice;

    if (choice == 2 || choice == 3)
    {
        cout << "Enter polynomial first\n0. Quit\n1. Enter Polynomial\n2. Print Polynomial\n3. Integrate\n\nEnter your choice: ";
        cin >> choice;
    }
    if (choice != 0 && choice != 1 && choice != 2 && choice != 3)
    {
        cout << "'" << choice << "'is an invalid choice\nEnter your choice : ";
        cin >> choice;
    }
return choice;
}

//This is the prototype that is going to loop after the first run
int getChoice()
{
    int choice;

    cin >> choice;

   while (choice != 0 && choice != 1 && choice != 2 && choice != 3)
    {
    cout << "'" << choice << "'is an invalid choice\nEnter your choice : ";
    cin >> choice;
   }
return choice;
}

int getN()
{
    int degree;

    cin >> degree;
    while (degree < 2 || degree > 10)
    {
        cout << "Enter degree of a polynom between 2 and 10 : \n";
        cin >> degree;
    }
    return degree;
}
double f(double x, double coef[], int n)
 {   //Evaluates the polynomial specified by n and coef[] at x.
 return 0;
}
double integral(double a, double b, double coef[], int n)
 {   //Evaluates the integral of the polynomial specified by coef[] and n from a to b.
return 0;
}
void print_polynomial(double coef[], int n)
{ cout<<coef[n]<<"*x^"<<n;
      for(int i=n-1;i>=2;i--)
          {if(coef[i]>0)
              cout<<"+"; 
          if(coef[i]!=0)
                if(coef[i]==1)
                     cout<<"x^"<<i;
                else
                    cout<<coef[i]<<"*x^"<<i;
                }   
      if(coef[1]>0)
              cout<<"+"; 
          if(coef[1]!=0)
                if(coef[1]==1)
                     cout<<"x ";
                else
                    cout<<coef[1]<<"*x ";
       if(coef[0]>0)
              cout<<"+"; 
       cout<<coef[0]; 
       cout<<endl<<endl;            

    //Do not print 1’s in front of coefficients except the first term.
}

Edited 6 Years Ago by gnarlyskim: n/a

I tried this to solve my integration issue, but it failed (not sure if I'm going on the right track):

double integral(double a, double b, double coef[], int n)
 {   //Evaluates the integral of the polynomial specified by coef[] and n from a to b.
     int d=n+1;
     int i;
     double hold1,hold2,sum1,sum2,final;

    cout << "Enter integration limits a b : ";
     cin >> a >> b;
     do
     {hold1=sum1;
     sum1=coef[i]*pow(a,d)/d;
     sum1+=hold1;
     } while (d>0);
     do
     {hold2=sum2;
     sum2=coef[i]*pow(b,d)/d;
     sum2+=hold2;
     final=sum1-sum2
     } while(d>0);
    return final;
}
printing term of polynomial without coeff if coeff == 1 and without exponents if exp  == 1 and without variable or exp if exp == 0:

if(coeff != 1)
  cout << coeff

if(exp > 1)
  cout << "x^" << exp;
else if(exp == 1)
  cout << "x";
//else if(exp == 0)
  //do nothing

solved my issue earlier today, had a 6 hour bus ride to bash my head against the laptop... Here's how i solved my printing issue(got the integration done but that was easy, I can help anyone that needs help with this):

void print_polynomial(double coef[], int n)
{
    if(coef[n]==1) cout << "x^"<<n;
    if(coef[n]==-1) cout<< "-x^"<<n;
    if(coef[n]>0 && coef[n]!=1) cout << coef[n]<<"*x^"<<n;
    if(coef[n]<0 && coef[n]!=-1) cout << coef[n]<<"*x^"<<n;

    for(int i=n-1;i>=2;i--)
    {
        if(coef[i]>0) cout<<"+";
        if(coef[i]==1) cout<<"x^"<<i;
        if(coef[i]==-1) cout<<"-x^"<<i;
        if(coef[i]<0 && coef[i]!=-1) cout<<coef[i]<<"*x^"<<i;
        if(coef[i]>0 && coef[i] !=1) cout<<coef[i]<<"*x^"<<i;
    }
    if(coef[1]==1) cout <<"+x";
    if(coef[1]==-1) cout<<"-x";
    if(coef[1]>0 && coef[1] !=1) cout<<"+"<<coef[1]<<"*x";
    if(coef[1]<0 && coef[1] !=-1) cout<<coef[1]<<"*x";

    if(coef[0]>0) cout<<"+"<<coef[0];
    if(coef[0]<0) cout<<coef[0];
}
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