IncPlusPlus/bigtoolbox-math

package io.github.incplusplus.bigtoolbox.math.differentialandintegratedcalculus;

import java.math.BigDecimal;
import java.util.Scanner;

/**
 * @author Ryan Cloherty
 */
public class Polynomial implements Function
{
    private int numTerms;
    private Term[] terms;
    private int degree;

    public Polynomial(Scanner in)
    {
        System.out.println("Beginning polynomial setup!");

        numTerms = Term.getIntAnswerGreaterThan("degree of polynomial", in, - 1) + 1;
        degree = numTerms - 1;
        terms = new Term[numTerms];
        //Start with the letter 'A'
        char letter = (char)65;
        for(int i = degree; i > 0; i--)
        {
            letter = (char)(65 + (degree - i));
            System.out.println(letter + "x^" + i);
            terms[degree - i] = new X(Term.getBigDecimalAnswer(String.valueOf(letter), in), i);
        }
        letter++;
        System.out.println(letter);
        //The last term should always be a constant
        terms[terms.length - 1] = new Constant(Term.getBigDecimalAnswer(String.valueOf(letter), in));

        System.out.println("Polynomial setup complete!");
    }

    public Polynomial(int numTerms, Term[] terms, int degree)
    {
        if(terms.length != numTerms)
        {
            System.out.println("numTerms != terms.length!!!!!");
            System.out.println("Length supposedly is " + numTerms);
            System.out.println("Length is actually " + terms.length);
            System.exit(0);
        }
        for(Term i : terms)
        {
            if(i instanceof X)
            {
                if(((X)i).getExponent() > degree)
                {
                    System.out.println("A term in terms has a degree that exceeds the maximum expected degree!!!!!");
                    System.exit(1);
                }
            }
        }
        this.numTerms = numTerms;
        this.terms = terms;
        this.degree = degree;
    }

    public BigDecimal f(BigDecimal x)
    {
        BigDecimal out = BigDecimal.ZERO;
        for(Term i : terms)
        {
            out = out.add(i.eval(x));
        }
        return out;
    }

    /**
     * Evaluation of the derivative of the polynomial at a certain x value
     *
     * @param x the value to substitute for x in the polynomial's integration
     * @return the y value of the integration of the polynomial at x
     */
    @Override
    public BigDecimal f_derived(BigDecimal x)
    {
        BigDecimal out = BigDecimal.ZERO;
        for(Term i : terms)
        {
            out = out.add(i.derivation(x));
        }
        return out;
    }

    public BigDecimal f_integrated(BigDecimal x)
    {
        BigDecimal out = BigDecimal.ZERO;
        for(Term i : terms)
        {
            out = out.add(i.integration(x));
        }
        return out;
    }

    public String getFormula()
    {
        String out = "";
        for(int i = 0; i < terms.length; i++)
        {
            if(! terms[i].getFormulaRepresentation().equals(""))
            {
                out += terms[i].getFormulaRepresentation();
                if(i < terms.length - 1)
                {
                    out += " + ";
                }
            }
        }
        //if(! terms[terms.length - 1].getFormulaRepresentation().equals(""))
        //{
        //    System.out.println(terms[terms.length - 1].getFormulaRepresentation());
        //    out += terms[terms.length - 1].getFormulaRepresentation();
        //}
        return out;
    }

    public String getIntegratedFormula()
    {
        String out = "";
        for(int i = 0; i < terms.length; i++)
        {
            if(! terms[i].getIntegratedRepresentation().equals(""))
            {
                out += terms[i].getIntegratedRepresentation();
                if(i < terms.length - 1)
                {
                    out += " + ";
                }
            }
        }
        //if(! terms[terms.length - 1].getIntegratedRepresentation().equals(""))
        //{
        //    out += " + " + terms[terms.length - 1].getIntegratedRepresentation();
        //}
        return out;
    }
}