Add basic Show capability

2 files changed, 164 insertions, 0 deletions

diff --git a/library/src/dotty/Show.scala b/library/src/dotty/Show.scala
new file mode 100644
index 000000000..123fffdc7
--- /dev/null
+++ b/library/src/dotty/Show.scala
@@ -0,0 +1,88 @@
+package dotty
+
+import scala.annotation.implicitNotFound
+
+@implicitNotFound("No member of type class Show could be found for ${T}")
+trait Show[-T] {
+  def show(t: T): String
+}
+
+object Show {
+  implicit class ShowValue[V](val v: V) extends AnyVal {
+    def show(implicit ev: Show[V] = null): String =
+      if (ev != null) ev.show(v)
+      else v.toString
+  }
+
+  implicit val stringShow = new Show[String] {
+    //charEscapeSeq ::= ‘\‘ (‘b‘ | ‘t‘ | ‘n‘ | ‘f‘ | ‘r‘ | ‘"‘ | ‘'‘ | ‘\‘)
+    def show(str: String) =
+      "\"" +
+      str
+      .replaceAll("\b", "\\\\b")
+      .replaceAll("\t", "\\\\t")
+      .replaceAll("\n", "\\\\n")
+      .replaceAll("\f", "\\\\f")
+      .replaceAll("\r", "\\\\r")
+      .replaceAll("\'", "\\\\'")
+      .replaceAll("\"", "\\\\\"") +
+      "\""
+  }
+
+  implicit val intShow = new Show[Int] {
+    def show(i: Int) = i.toString
+  }
+
+  implicit val floatShow = new Show[Float] {
+    def show(f: Float) = f + "f"
+  }
+
+  implicit val doubleShow = new Show[Double] {
+    def show(d: Double) = d.toString
+  }
+
+  implicit val charShow = new Show[Char] {
+    def show(c: Char) = "'" + (c match {
+      case '\b' => "\\b"
+      case '\t' => "\\t"
+      case '\n' => "\\n"
+      case '\f' => "\\f"
+      case '\r' => "\\r"
+      case '\'' => "\\'"
+      case '\"' => "\\\""
+      case c    => c
+    }) + "'"
+  }
+
+  object List {
+    implicit def showList[T](implicit st: Show[T]) = new Show[List[T]] {
+      def show(xs: List[T]) =
+        if (xs.isEmpty) "Nil"
+        else "List(" + xs.map(_.show).mkString(", ") + ")"
+    }
+
+    implicit val showNil = new Show[List[Nothing]] {
+      def show(xs: List[Nothing]) = "Nil"
+    }
+  }
+
+  object Option {
+    implicit def showOption[T](implicit st: Show[T]) = new Show[Option[T]] {
+      def show(ot: Option[T]): String = ot match {
+        case Some(t) => "Some("+ st.show(t) + ")"
+        case none => "None"
+      }
+    }
+
+    implicit val showNone = new Show[Option[Nothing]] {
+      def show(n: Option[Nothing]) = "None"
+    }
+  }
+
+  object Map {
+    implicit def showMap[K, V](implicit sk: Show[K], sv: Show[V]) = new Show[Map[K, V]] {
+      def show(m: Map[K, V]) =
+        "Map(" + m.map { case (k, v) => sk.show(k) + " -> " + sv.show(v) } .mkString (", ") + ")"
+    }
+  }
+}
diff --git a/library/test/dotty/ShowTests.scala b/library/test/dotty/ShowTests.scala
new file mode 100644
index 000000000..ef259e5d8
--- /dev/null
+++ b/library/test/dotty/ShowTests.scala
@@ -0,0 +1,76 @@
+package dotty
+
+import org.junit.Test
+import org.junit.Assert._
+
+class ShowTests {
+  import Show._
+
+  @Test def showString = {
+    assertEquals("\"\\thello world!\"", "\thello world!".show)
+    assertEquals("\"\\nhello world!\"", "\nhello world!".show)
+    assertEquals("\"\\rhello world!\"", "\rhello world!".show)
+    assertEquals("\"\\b\\t\\n\\f\\r\\\'\\\"\"", "\b\t\n\f\r\'\"".show)
+  }
+
+  @Test def showFloat = {
+    assertEquals("1.0f", 1.0f.show)
+    assertEquals("1.0f", 1.0F.show)
+  }
+
+  @Test def showDouble = {
+    assertEquals("1.0", 1.0d.show)
+    assertEquals("1.0", 1.0.show)
+  }
+
+  @Test def showChar = {
+    assertEquals("'\\b'", '\b'.show)
+    assertEquals("'\\t'", '\t'.show)
+    assertEquals("'\\n'", '\n'.show)
+    assertEquals("'\\f'", '\f'.show)
+    assertEquals("'\\r'", '\r'.show)
+    assertEquals("'\\''", '\''.show)
+    assertEquals("'\\\"'", '\"'.show)
+  }
+
+  @Test def showCar = {
+    import Show.List._
+    case class Car(model: String, manufacturer: String, year: Int)
+    implicit val showCar = new Show[Car] {
+      def show(c: Car) =
+        "Car(" + c.model.show + ", " + c.manufacturer.show + ", " + c.year.show + ")"
+    }
+
+    case class Shop(xs: List[Car], name: String)
+    implicit val showShop = new Show[Shop] {
+      def show(sh: Shop) =
+        "Shop(" + sh.xs.show + ", " + sh.name.show + ")"
+    }
+
+    assertEquals("Car(\"Mustang\", \"Ford\", 1967)", Car("Mustang", "Ford", 1967).show)
+  }
+
+  @Test def showOptions = {
+    import Show.Option._
+    // TODO: first case is not possible since there's no Show[Nothing] - yet
+    //assertEquals("None", None.show)
+    assertEquals("None", (None: Option[String]).show)
+    assertEquals("Some(\"hello opt\")", Some("hello opt").show)
+  }
+
+  @Test def showMaps = {
+    import Show.Map._
+    val mp = scala.collection.immutable.Map("str1" -> "val1", "str2" -> "val2")
+    assertEquals("Map(\"str1\" -> \"val1\", \"str2\" -> \"val2\")", mp.show)
+  }
+
+  @Test def withoutShow = {
+    case class Car(model: String, manufacturer: String, year: Int)
+
+    assertEquals("Car(Mustang,Ford,1967)", Car("Mustang", "Ford", 1967).show)
+    assertEquals(
+      "Map(str1 -> val1, str2 -> val2)",
+      scala.collection.immutable.Map("str1" -> "val1", "str2" -> "val2").show
+    )
+  }
+}