1 files changed, 50 insertions, 0 deletions
diff --git a/examples/src/main/scala/eq.scala b/examples/src/main/scala/eq.scala
new file mode 100644
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+++ b/examples/src/main/scala/eq.scala
@@ -0,0 +1,50 @@
+package magnolia.examples
+
+import magnolia._
+
+import language.experimental.macros
+import collection.immutable.ListMap
+
+object `package` {
+  implicit class Equable[T: Eq](t: T) {
+    def isEqualTo(other: T): Boolean = implicitly[Eq[T]].isEqual(t, other)
+  }
+  
+  implicit val eqString: Eq[String] = _ == _
+  implicit val eqBool: Eq[Boolean] = _ == _
+  
+  implicit def eqList[T: Eq]: Eq[List[T]] =
+    (l1, l2) => l1.size == l2.size && (l1 zip l2).forall { case (e1, e2) => e1 isEqualTo e2 }
+
+  implicit def eqSet[T: Eq]: Eq[Set[T]] =
+    (s1, s2) => s1.size == s2.size && (s1 zip s2).forall { case (e1, e2) => e1 isEqualTo e2 }
+}
+
+sealed trait Tree
+case class Branch(left: Tree, right: Tree) extends Tree
+case class Leaf(value: Int) extends Tree
+
+sealed trait Entity
+case class Person(name: String, address: Address) extends Entity
+case class Organization(name: String, contacts: Set[Person]) extends Entity
+case class Address(lines: List[String], country: Country)
+case class Country(name: String, code: String, salesTax: Boolean)
+
+trait Eq[T] { def isEqual(a: T, b: T): Boolean }
+
+object Eq {
+
+  implicit val eqInt: Eq[Int] = _ == _
+
+  implicit val derivation: ContravariantDerivation2[Eq] = new ContravariantDerivation2[Eq] {
+    type Return = Boolean
+    
+    def call[T](eq: Eq[T], value1: T, value2: T): Boolean =
+      if(value1.getClass == value2.getClass) eq.isEqual(value1, value2) else false
+    
+    def construct[T](body: (T, T) => Boolean): Eq[T] = body(_, _)
+    def join(elements: ListMap[String, Boolean]): Boolean = elements.forall(_._2)
+  }
+  
+  implicit def generic[T]: Eq[T] = macro Macros.magnolia[T, Eq[_]]
+}