package question2;

/*represents a polynomial with a
 *  degree and coefficients
 *  can have a whole number degree
 *  and a array of coefficients sized based on degree
 */
public class Polynomial {

    int degree;
    double[] coefficients;

/*
 * regular constructor for polynomial
 * only fills the degree variable of object
 */
public Polynomial(int deg) {
    degree=deg;
    coefficients=new double[deg+1];
}

/*
 * copy constructor
 */
public Polynomial(Polynomial p) {
    this.degree=p.degree;
    this.coefficients=p.coefficients;
}

/*
 * sets value of coefficient in array, use in loop the index
 * is the number of coefficients in polynomial equation
 * based on standard polynomial equation
 */
public void setCoefficient(int index, double value) {
    coefficients[index]=value;
}

/*
 * supply value of coefficient from array, use in loop
 */
public double getCoefficient(int index) {
    double value=this.coefficients[index];
    return value;
}

/*
 * Calculates y of fully constructed polynomial given a x
 */
public double evaluate(double x){
    double value=this.coefficients[0];
    for(int i=0; i<=this.degree; i++) {
        value=value+(  (this.coefficients[i])  *   (Math.pow(x, i))    );
    }
    return value;

}

/*
 * Determines if two polynomials are equal
 * compares degree and coefficients in order
 */
public boolean equals(Polynomial poly) {
    boolean isOrdered=false;

    if(poly.degree==this.degree) {
        for(int i=0; i<this.degree; i++) {
            if(this.coefficients[i]==poly.coefficients[i]) {
            isOrdered=true; }
            else {
                isOrdered=false; }

        }
    }
if(isOrdered) {
    return true;
}
else {
    return false;
}

}


/*
 * converts polynomial to string
 * as visual of equation
 */
public String toString() {
    String out=""+this.coefficients[0];


    for(int i=1; i<=this.degree; i++) {
        if(this.coefficients[i]>0)
        out=out+" + ("+this.coefficients[i]+")x^"+i;
    }
    return out;
}

}
--------------------------------------------------------------------
package question2;
import java.util.Scanner;

public class PolynomialTester {

    public static void main(String[] args) {

        Scanner keyb= new Scanner(System.in);

        System.out.print("Enter degree of polynomial: ");
        int degree=keyb.nextInt();
        if(degree<=0) {
            System.out.print("Invalid degree, re-enter: ");
            degree=keyb.nextInt();
        }

        Polynomial poly1=new Polynomial(degree);
        double input;

        for(int i=0; i<=degree; i++) {
            System.out.print("Enter Coeff for degree "+i+": ");
            input=keyb.nextDouble();
            poly1.setCoefficient(i, input);
        }

        System.out.print("Polynomial: "+poly1.toString());
        boolean exit=false;
        String userInput="";
        double x=0;

        do {
            System.out.println();
            System.out.print("Enter a value of x for which to evaluate the polynomial: ");
            userInput=keyb.next();
            try {
                x=Double.parseDouble(userInput);
                System.out.print("For x ="+x+", polynomial = "+poly1.evaluate(x));
            }catch (NumberFormatException e){
                if (userInput.compareTo("quit") == 0) {
                    exit = true;
                }
                else {
                    exit = false;
                }
            }
        }while(!exit);

        System.out.print("Created copy of polynomial");
        Polynomial poly2=new Polynomial(poly1);
        System.out.println();
        System.out.print("Polynomials are equal: "+poly1.equals(poly2));
        System.out.println();
        System.out.println("To make them unequal enter a index and coefficent to change:");
        int index=keyb.nextInt();
        input=keyb.nextDouble();
        poly2.setCoefficient(index, input);
        System.out.print("Polynomials are equal: "+poly1.equals(poly2));
    }
}