From d3bf8bef81124ef47097d808a0b9299641fe5c7b Mon Sep 17 00:00:00 2001
From: Rui Gonçalves <ruippeixotog@gmail.com>
Date: Wed, 21 Jun 2017 22:39:26 +0100
Subject: Add ContravariantDerivation for cats.Show

---
 examples/src/main/scala/cats.scala | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)
 create mode 100644 examples/src/main/scala/cats.scala

(limited to 'examples')

diff --git a/examples/src/main/scala/cats.scala b/examples/src/main/scala/cats.scala
new file mode 100644
index 0000000..08690c2
--- /dev/null
+++ b/examples/src/main/scala/cats.scala
@@ -0,0 +1,23 @@
+package magnolia.examples.cats
+
+import scala.collection.immutable.ListMap
+import scala.language.experimental.macros
+import scala.language.higherKinds
+
+import cats.Show
+import magnolia.ContravariantDerivation
+import magnolia.Macros
+
+object instances extends instances1 {
+
+  implicit val showDerivation = new ContravariantDerivation[Show] {
+    type Return = String
+    def call[T](show: Show[T], value: T): String = show.show(value)
+    def construct[T](body: T => String): Show[T] = body(_)
+    def join(xs: ListMap[String, String]): String = xs.map { case (k, v) => s"$k=$v" }.mkString("{", ", ", "}")
+  }
+}
+
+trait instances1 {
+  implicit def genericShow[T]: Show[T] = macro Macros.magnolia[T, Show[_]]
+}
-- 
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