package jfractionse;

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */

/**
 *
 * @author gabriele
 */


public class fraction {

 private int n;
 private int d;

 public fraction() {
   this.n = this.d = 1;
 }

 public fraction(int a) {
   this.n=a;
   this.d=1;
 }

 fraction(int a, int b)throws IllegalArgumentException {
    if (b==0) {
       throw new IllegalArgumentException();

    } else {
       this.n = a;
       this.d = b;
       this.reduce();
    }
 }


 // test di positivita'
 public boolean is_pos(){
   return (this.n > 0);
 }


 // operazioni di lettura
 public int get_numerator() {
    return this.n;
 }

 public int get_denumerator() {
    return this.d;
 }

  // operazioni di scrittura
 public void set_numerator(int a) {
    this.n=a;
    this.reduce();
 }

 public void set_denumerator(int a) throws IllegalArgumentException {
    if (a==0) {
       throw new IllegalArgumentException();
    }

    this.d = a;
    this.reduce();
 }

 // operazioni aritmetiche
 public fraction sum(fraction f) {
    fraction tmp= new fraction();
    tmp.n = this.n * f.d + this.d * f.n;
    tmp.d = this.d * f.d;
    tmp.reduce();
    return tmp;
 }

 public fraction sub(fraction  f) {
    fraction tmp= new fraction();
    tmp.n = this.n * f.d - this.d * f.n;
    tmp.d = this.d * f.d;
    tmp.reduce();
    return tmp;
 }

 public fraction mul(fraction f) {
    fraction tmp = new fraction();
    tmp.n = this.n * f.n;
    tmp.d = this.d * f.d;
    tmp.reduce();
    return tmp;
 }

 public fraction div(fraction  f) throws IllegalArgumentException {
    if (f.n==0) {
       throw new IllegalArgumentException();
    }

    fraction x = new fraction(f.d,f.n);
    return this.mul(x);
    }


  public String toString() {
        return " " + this.n +"/"+ this.d +" ";
  }

 //---------------------------------------------------
 // funzione di utilita'
 //---------------------------------------------------
private void reduce() {
    if ( this.n == 0 ) {  // frazione uguale a zero
       this.d=1;
       return;
    }

    if ( this.d < 0 ) {    // rendo il denominatore positivo
       this.n *= -1;
       this.d *= -1;
    }

    int nn=this.n;
    int dd=this.d;   //dd e' sicuramente positivo

    if (nn <0 ) nn= - nn; //rendo nn positivo


    while ( nn != dd )  { //applico l'algoritmo di Euclide

        if ( nn > dd )
           nn -= dd;
        else
           dd -= nn;
    }

    this.n /= nn;
    this.d /= nn;
 }


}