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-rw-r--r--projects/09/Fraction/Fraction.jack65
-rw-r--r--projects/09/Fraction/Main.jack16
2 files changed, 81 insertions, 0 deletions
diff --git a/projects/09/Fraction/Fraction.jack b/projects/09/Fraction/Fraction.jack
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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;
+ }
+}
diff --git a/projects/09/Fraction/Main.jack b/projects/09/Fraction/Main.jack
new file mode 100644
index 0000000..43ddece
--- /dev/null
+++ b/projects/09/Fraction/Main.jack
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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/Main.jack
+
+// Computes the sum of 2/3 and 1/5.
+class Main {
+ function void main() {
+ var Fraction a, b, c;
+ let a = Fraction.new(2,3);
+ let b = Fraction.new(1,5);
+ let c = a.plus(b); // Computes c = a + b
+ do c.print(); // Prints "13/15"
+ return;
+ }
+}