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// This file is part of www.nand2tetris.org
// and the book "The Elements of Computing Systems"
// by Nisan and Schocken, MIT Press.
// File name: projects/09/Fraction/Fraction.jack
/** Represents the Fraction type and related operations. */
class Fraction {
field int numerator, denominator; // field = property = member variable.
/** Constructs a (reduced) fraction from the given numerator and denominator. */
constructor Fraction new(int x, int y) {
let numerator = x;
let denominator = y;
do reduce(); // reduces the fraction
return this; // a constructor is expected to return a reference to the new object
}
// Reduces this fraction.
method void reduce() {
var int g;
let g = Fraction.gcd(numerator, denominator);
if (g > 1) {
let numerator = numerator / g;
let denominator = denominator / g;
}
return;
}
/** Accessors. */
method int getNumerator() { return numerator; }
method int getDenominator() { return denominator; }
/** Returns the sum of this fraction and the other one. */
method Fraction plus(Fraction other) {
var int sum;
let sum = (numerator * other.getDenominator()) + (other.getNumerator() * denominator);
return Fraction.new(sum, denominator * other.getDenominator());
}
// More fraction-related methods (minus, times, div, etc.) can be added here.
/** Disposes this fraction. */
method void dispose() {
do Memory.deAlloc(this); // uses an OS routine to recycle the memory held by the object
return;
}
/** Prints this fraction in the format x/y. */
method void print() {
do Output.printInt(numerator);
do Output.printString("/");
do Output.printInt(denominator);
return;
}
// Computes the greatest common divisor of the given integers.
function int gcd(int a, int b) {
var int r;
while (~(b = 0)) { // applies Euclid's algorithm
let r = a - (b * (a / b)); // r = remainder of the integer division a/b
let a = b; let b = r;
}
return a;
}
}
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