From a000308104aab27c2dde9a306f1bc654b2db4806 Mon Sep 17 00:00:00 2001
From: Yuchen Pei <me@ypei.me>
Date: Wed, 29 Nov 2017 12:30:41 +0100
Subject: first commit

---
 projects/09/Fraction/Fraction.jack | 65 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)
 create mode 100644 projects/09/Fraction/Fraction.jack

(limited to 'projects/09/Fraction/Fraction.jack')

diff --git a/projects/09/Fraction/Fraction.jack b/projects/09/Fraction/Fraction.jack
new file mode 100644
index 0000000..c86f0a5
--- /dev/null
+++ b/projects/09/Fraction/Fraction.jack
@@ -0,0 +1,65 @@
+// 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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