added rationals

src/Lesson3/Rational.sc

@@ -0,0 +1,21 @@
+class Rational(n: Int, d: Int) {
+  def num = n
+  def denom = d
+}
+
+def add(x: Rational, y: Rational): Rational =
+  new Rational(
+    x.num * y.denom + x.denom * y.num,
+    x.denom * y.denom
+  )
+
+def stringVersion(x: Rational) = x.num + "/" + x.denom
+
+val r1 = new Rational(1, 2)
+r1.num
+r1.denom
+
+val r2 = new Rational(3, 4)
+
+val r3 = add(r1, r2)
+stringVersion(r3)