First commit

chapter4/fraction.ex

@@ -0,0 +1,16 @@
+defmodule Fraction do
+  defstruct a: nil, b: nil
+
+  def new(a, b), do: %Fraction{a: a, b: b}
+
+  def value(%Fraction{a: a, b: b}) do
+    a / b
+  end
+
+  def add(%Fraction{a: a1, b: b1}, %Fraction{a: a2, b: b2}) do
+    new(
+      a1 * b2 + a2 * b1,
+      b1 * b2
+    )
+  end
+end