From efe29cc831ad29910cbae77e19e4c63d318b2167 Mon Sep 17 00:00:00 2001
From: Zhenia Trochun <zheniatrochun@gmail.com>
Date: Sun, 10 Jun 2018 16:44:48 +0300
Subject: [PATCH] Added Scala examples

---
 Scala/.gitignore          |  3 +++
 Scala/1-functor.scala     | 25 +++++++++++++++++++++++++
 Scala/2-not-functor.scala | 17 +++++++++++++++++
 Scala/3-maybe.scala       | 27 +++++++++++++++++++++++++++
 Scala/README.md           |  4 ++++
 5 files changed, 76 insertions(+)
 create mode 100644 Scala/.gitignore
 create mode 100644 Scala/1-functor.scala
 create mode 100644 Scala/2-not-functor.scala
 create mode 100644 Scala/3-maybe.scala
 create mode 100644 Scala/README.md

diff --git a/Scala/.gitignore b/Scala/.gitignore
new file mode 100644
index 0000000..b4a5277
--- /dev/null
+++ b/Scala/.gitignore
@@ -0,0 +1,3 @@
+.idea/
+target/
+*.iml
diff --git a/Scala/1-functor.scala b/Scala/1-functor.scala
new file mode 100644
index 0000000..b960d1f
--- /dev/null
+++ b/Scala/1-functor.scala
@@ -0,0 +1,25 @@
+/**
+  * Simple functor example
+  */
+
+case class Functor[A](x: A) {
+  def map[B](f: (A) => B): Functor[B] = Functor(f(x))
+}
+
+object Example {
+
+  def main(args: Array[String]): Unit = {
+    val functor = Functor(2)
+
+    println("Functor rules")
+
+    println("1. functor.map(x => x) = functor")
+    println(s"functor.map(x => x) = ${functor.map(x => x)}")
+    println(s"functor = $functor")
+
+    println("2. functor.map(x => f(g(x))) = functor.map(g).map(f)")
+    println(s"functor.map(x => f(g(x))) = ${functor.map(x => (x * 2) * 3)}")
+    println(s"functor.map(g).map(f) = ${functor.map(_ * 2).map(_ * 3)}")
+
+  }
+}
diff --git a/Scala/2-not-functor.scala b/Scala/2-not-functor.scala
new file mode 100644
index 0000000..79b9c8a
--- /dev/null
+++ b/Scala/2-not-functor.scala
@@ -0,0 +1,17 @@
+/**
+  * NOT a functor because map method returns just value, not ValueMapper
+  */
+
+case class ValueMapper[A](x: A) {
+  def map[B](f: (A) => B): B =
+    f(x)
+}
+
+object NotFunctorExample {
+
+  def main(args: Array[String]): Unit = {
+    val mapper = ValueMapper("Hello" -> 123)
+
+    println(mapper.map(_._1.toUpperCase))
+  }
+}
diff --git a/Scala/3-maybe.scala b/Scala/3-maybe.scala
new file mode 100644
index 0000000..de54c76
--- /dev/null
+++ b/Scala/3-maybe.scala
@@ -0,0 +1,27 @@
+case class Maybe[A](x: Option[A]) {
+  def map[B](f: (A) => B): Maybe[B] =
+    Maybe(x.map(f))
+
+  def isNothing = x.isEmpty
+
+  override def toString: String =
+    if (isNothing) "Maybe(Nothing)"
+    else s"Maybe(${x.get})"
+}
+
+object Maybe {
+  def apply[A](x: A): Maybe[A] = Maybe(Some(x))
+
+  def empty[A]: Maybe[A] = Maybe[A](None)
+}
+
+object ExampleMaybe {
+
+  def main(args: Array[String]): Unit = {
+    val empty = Maybe.empty[Int]
+    val notEmpty = Maybe(2)
+
+    println(s"Expect Nothing, actual = ${empty.map(_ => 3)}")
+    println(s"Expect Maybe(3), actual = ${notEmpty.map(_ => 3)}")
+  }
+}
diff --git a/Scala/README.md b/Scala/README.md
new file mode 100644
index 0000000..828373b
--- /dev/null
+++ b/Scala/README.md
@@ -0,0 +1,4 @@
+## Scala examples of Functor
+Some great articles:
+1. [What is a functor?](https://medium.com/@dtinth/what-is-a-functor-dcf510b098b6)
+2. [What's NOT a functor](https://medium.com/@dtinth/what-s-not-a-functor-57a081131555)
\ No newline at end of file