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Program To Add To Polynomials by logic101: 10:39pm On Jul 25, 2011 |
Hi am a computer science student working on a particular question to perform certain functions with polynomials.I have two classes, my monomial class and my polynomial class. I am trying to add two polynomials but i keep gtting a null pointer exception in my add method.Can the house help , Fayimora u seem well infromed can you chip in . public class Polynimial { Monomial [] polynomial;; int degree; Scanner in= new Scanner(System.in); // int a is coefficient while int b is the exponent public Polynimial(int c){ polynomial= new Monomial[c+1]; } public static void main(String[] args) { Polynimial c= new Polynimial(1); c.setPolynomial(); Polynimial d = new Polynimial(1); d.setPolynomial(); System.out.println(c.plus(d)); } public void setPolynomial(){ int x=polynomial.length; int count=0; System.out.println("please enter in this particular order all the coefficient and exponent " while(count<x){ int coefficient=in.nextInt(); int exponent=in.nextInt(); polynomial[exponent]=new Monomial(coefficient,exponent); count++; } } public int getHighestDegree(){ int c= polynomial.length ; return c; } public Polynimial plus(Polynimial c){ Polynimial result = new Polynimial(Math.max(this.getHighestDegree(), c.getHighestDegree())); int x=0; for(int i=0;i<result.getHighestDegree();i++){ x=polynomial[i].addMonomials( c.polynomial[i]); result.polynomial[i].setCoefficient(x); } return result; } } public class Monomial { private int coefficient; private int exponent; public Monomial(int c,int e){ coefficient=c; exponent=e; } public int getCoefficient(){ return coefficient; } public int getExponent(){ return exponent; } public int addMonomials(Monomial c){ int sum =0; if(this.exponent==c.exponent) sum= (this.coefficient + c.coefficient); return sum; } public int subPolynomials(Monomial c){ int diff=0; if(this.exponent==c.exponent) diff= this.coefficient - c.coefficient; return diff; } public void setCoefficient(int y){ coefficient=y; } } |
Re: Program To Add To Polynomials by Fayimora(m): 10:49pm On Jul 25, 2011 |
How are we suposed to enter in the 'polynimial'. Use this ==> 2x3 + 2x2 + 4x + 1 = 0 So how do I key in the values? Also, you got some really bad names here that can cause a brain damage, lol Just kidding but your variable names are confusing, |
Re: Program To Add To Polynomials by logic101: 10:54pm On Jul 25, 2011 |
lol fayimora yup my variable names are u knwww, i would take that into consideration lol, u can key in the values in the main program which is in the polynomial class, |
Re: Program To Add To Polynomials by Fayimora(m): 10:56pm On Jul 25, 2011 |
No i mean during execution. You have this: What do i key in(use the example above), that instruction is not descriptive enough! |
Re: Program To Add To Polynomials by logic101: 11:04pm On Jul 25, 2011 |
oh alryt e.g lets say u want to add 5x^3 + 2X^2 + 2x +9 and 4x^3 + 2X^2+7x +5 for first polynomial u wld entr the max exponent of each polynomial into its object reference, so it can be input in to ways frm exponent o which wld be coefficient, exponent 9 0 2 1 2 2 5 3 |
Re: Program To Add To Polynomials by Fayimora(m): 11:08pm On Jul 25, 2011 |
Well the bad news is that you have more problems than you thought public void setPolynomial(){ Help me to understand why you have this: int x=polynomial.length; |
Re: Program To Add To Polynomials by logic101: 11:13pm On Jul 25, 2011 |
its used in the while loop as a condition to input the coefficientss so if the lenght of the polynomial is 6, it needs 6 coefficients starting frm index 0-5 |
Re: Program To Add To Polynomials by Fayimora(m): 11:18pm On Jul 25, 2011 |
But i dnt see where you check the length of the polynomial, Weird! Do you mind re-writing this code? They are easier ways to do this i guess. Do you have a requirement or you just have to implement in in anyway. If you dont have a requirement then the fastest way to do this is with a Map. Do you want to re-write it? Don't worr about not knowing how to use a map I would walk you through the whole process, but you would do the reasoning part. Reason why i want you to rewrite the code is because what you have here has a lot of redundancies and its very confusing(e.g you called a variable of type Monomial `polynomial`) Its just difficult to comprehend. |
Re: Program To Add To Polynomials by Fayimora(m): 4:22am On Jul 26, 2011 |
Hey sorry was baned by the spambot, Have a look at what i posted which is marked as spam |
Re: Program To Add To Polynomials by Nobody: 5:46pm On Aug 02, 2011 |
Hey i am not sure if this is what u want, but i once did a programming assignment like this in C++ for a polynomial class years ago, u gonna have to decipher it yourself cause i don't really have time, Below is the source code, If i recall, i think i used a lot of container classes and pointers #include <iostream> #include <cassert> #include <math.h> #include "Poly.h" using namespace std; //------------------------Term member functions------------------------------ Term::Term(double c, int e) : coeff(c), expon(e) { assert(expon >= 0); } Term::Term() : coeff(0), expon(0) { } //------------------------Poly member functions------------------------------ Poly::Poly() { } Poly::Poly(Term t) { //want to store non-zero co-efficients only in list of type Term if(t.coeff != 0) data.push_back(t); } list <Term> Poly::getdata() { return data; } void Poly::operator += (const Poly &b) { list<Term>::const_iterator bpos = b.data.begin(); //iterator returns pointer to current b element list<Term>::iterator apos = data.begin(); double coefficient; int exponent; bool flag = 0; for( apos = data.begin(); apos!= data.end(); apos++) { if(apos->expon == bpos->expon && apos->coeff == bpos->coeff) { flag = true; bpos++; } else { flag = false; break; } } if( data.size() == b.data.size() && flag == true) //special case { //cout<<"equal list "<<end; list<Term>::iterator tempIter; for(apos = data.begin(); apos!= data.end();apos++) { exponent = apos->expon; coefficient = 2*(apos->coeff); Term newterm(coefficient, exponent); //have to erase old value so do some pointer saving etc tempIter = data.erase(apos); apos = tempIter; // apos--; if(newterm.coeff != 0) { data.insert(tempIter, newterm); apos--; } } } else{ for(apos = data.begin(); bpos!= b.data.end() && apos != data.end() { if( apos->expon < bpos->expon) { apos++; //cout<<"not inserting "<<endl; } else if (apos->expon == bpos->expon) { //cout<<"here 1"<<endl; coefficient = apos->coeff + bpos->coeff; //cout<<"new coeff is "<<coefficient<<endl; exponent = apos->expon; //Now construct new data term Term newTerm(coefficient, exponent); //save current pointers list<Term>::iterator apos1 = apos; list<Term>::const_iterator bpos1 = bpos; apos1 = data.erase(apos); //removes current element and returns position of next apos = apos1; //now assign apos back since we used in controlling loop apos--; bpos++; //advance bpos by 1 to ignore value that has been added to new term //check to make sure we only insert non-zero coefficients in list //cout<<"newterm coefficient is "<<newTerm.coeff<<endl; if(newTerm.coeff != 0) { data.insert(apos1,newTerm); } } else { data.insert(apos,*bpos); //cout<<"inserting "<<endl; bpos++; } } if(apos == data.end() && bpos != b.data.end()) //not done { while(bpos != b.data.end()) { data.insert(apos,*bpos); bpos++; //cout<<"here 2"<<endl; } } } } float Poly::eval(double x) const //accessor function { float value = 0; list<Term>::const_iterator epos = data.begin(); while(epos != data.end()) { value = value + (epos->coeff)*( pow(x,epos->expon)); epos++; } return value; } void Poly::print(ostream &out) const { list<Term>::const_iterator pos; for(pos = data.begin(); pos!=data.end(); pos++) { int e = pos->expon; double c = pos->coeff; if(c > 0) out << " + "; out << c; if(e > 0) out << "x"; if(e > 1) out <<"^"<<e; } out<<endl; } //--------------------Poly non-member functions------------------------- // we're writing << operator for you in terms of the member function print // you just need to write print ostream & operator << (ostream &out, const Poly &p) { p.print(out); return out; // all overloaded << ops must return the stream } Poly operator + (const Poly &a, const Poly &b) // add two Poly's { Poly p = Poly(); //creates empty polynomial p+=a; p+=b; return p; } BELOW IS THE HEADER FILE Poly.h #ifndef POLY_H #define POLY_H #include <iostream> #include <list> using namespace std; struct Term { Term(); Term (double c, int e); double coeff; int expon; }; class Poly { public: Poly (); // creates 0 polynomial Poly(Term t); // creates polynomial with single term t void operator += (const Poly &b); // add b to polynomial float eval (double x) const; // evaluate polynomial at given value of x void print(ostream &out) const; list <Term> getdata(); //returns list of current polynomial private: list <Term> data; // you may want to add auxiliary member functions here void add_data(Term a); }; // non member functions on Poly: Poly operator + (const Poly &a, const Poly &b); // add two Poly's ostream & operator << (ostream &out, const Poly &p); #endif |
Re: Program To Add To Polynomials by logic101: 7:47pm On Aug 02, 2011 |
Thanks for your contribution i appreciat eit |
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