scalajs cross build

4 files changed, 218 insertions, 0 deletions

diff --git a/examples/shared/src/main/scala/decode.scala b/examples/shared/src/main/scala/decode.scala
new file mode 100644
index 0000000..5b083bd
--- /dev/null
+++ b/examples/shared/src/main/scala/decode.scala
@@ -0,0 +1,79 @@
+package magnolia.examples
+
+import magnolia._
+import scala.language.experimental.macros
+
+/** very basic decoder for converting strings to other types */
+trait Decoder[T] { def decode(str: String): T }
+
+/** derivation object (and companion object) for [[Decoder]] instances */
+object Decoder {
+
+  /** decodes strings */
+  implicit val string: Decoder[String] = new Decoder[String] {
+    def decode(str: String): String = str
+  }
+
+  /** decodes ints */
+  implicit val int: Decoder[Int] = new Decoder[Int] { def decode(str: String): Int = str.toInt }
+
+  /** binds the Magnolia macro to this derivation object */
+  implicit def gen[T]: Decoder[T] = macro Magnolia.gen[T]
+
+  /** type constructor for new instances of the typeclass */
+  type Typeclass[T] = Decoder[T]
+
+  /** defines how new [[Decoder]]s for case classes should be constructed */
+  def combine[T](ctx: CaseClass[Decoder, T]): Decoder[T] = new Decoder[T] {
+    def decode(value: String) = {
+      val (name, values) = parse(value)
+      ctx.construct { param =>
+        param.typeclass.decode(values(param.label))
+      }
+    }
+  }
+
+  /** defines how to choose which subtype of the sealed trait to use for decoding */
+  def dispatch[T](ctx: SealedTrait[Decoder, T]): Decoder[T] = new Decoder[T] {
+    def decode(param: String) = {
+      val (name, values) = parse(param)
+      val subtype = ctx.subtypes.find(_.label == name).get
+      subtype.typeclass.decode(param)
+    }
+  }
+
+  /** very simple extractor for grabbing an entire parameter value, assuming matching parentheses */
+  private def parse(value: String): (String, Map[String, String]) = {
+    val end = value.indexOf('(')
+    val name = value.substring(0, end)
+
+    def parts(value: String,
+              idx: Int = 0,
+              depth: Int = 0,
+              collected: List[String] = List("")): List[String] = {
+      def plus(char: Char): List[String] = collected.head + char :: collected.tail
+
+      if (idx == value.length) collected
+      else
+        value(idx) match {
+          case '(' =>
+            parts(value, idx + 1, depth + 1, plus('('))
+          case ')' =>
+            if (depth == 1) plus(')')
+            else parts(value, idx + 1, depth - 1, plus(')'))
+          case ',' =>
+            if (depth == 0) parts(value, idx + 1, depth, "" :: collected)
+            else parts(value, idx + 1, depth, plus(','))
+          case char =>
+            parts(value, idx + 1, depth, plus(char))
+        }
+    }
+
+    def keyValue(str: String): (String, String) = {
+      val List(label, value) = str.split("=", 2).to[List]
+      (label, value)
+    }
+
+    (name, parts(value.substring(end + 1, value.length - 1)).map(keyValue).toMap)
+  }
+}
diff --git a/examples/shared/src/main/scala/default.scala b/examples/shared/src/main/scala/default.scala
new file mode 100644
index 0000000..4c1b634
--- /dev/null
+++ b/examples/shared/src/main/scala/default.scala
@@ -0,0 +1,35 @@
+package magnolia.examples
+
+import magnolia._
+import scala.language.experimental.macros
+
+/** typeclass for providing a default value for a particular type */
+trait Default[T] { def default: T }
+
+/** companion object and derivation object for [[Default]] */
+object Default {
+
+  type Typeclass[T] = Default[T]
+
+  /** constructs a default for each parameter, using the constructor default (if provided),
+    *  otherwise using a typeclass-provided default */
+  def combine[T](ctx: CaseClass[Default, T]): Default[T] = new Default[T] {
+    def default = ctx.construct { param =>
+      param.default.getOrElse(param.typeclass.default)
+    }
+  }
+
+  /** chooses which subtype to delegate to */
+  def dispatch[T](ctx: SealedTrait[Default, T])(): Default[T] = new Default[T] {
+    def default: T = ctx.subtypes.head.typeclass.default
+  }
+
+  /** default value for a string; the empty string */
+  implicit val string: Default[String] = new Default[String] { def default = "" }
+
+  /** default value for ints; 0 */
+  implicit val int: Default[Int] = new Default[Int] { def default = 0 }
+
+  /** generates default instances of [[Default]] for case classes and sealed traits */
+  implicit def gen[T]: Default[T] = macro Magnolia.gen[T]
+}
diff --git a/examples/shared/src/main/scala/eq.scala b/examples/shared/src/main/scala/eq.scala
new file mode 100644
index 0000000..8ee42a4
--- /dev/null
+++ b/examples/shared/src/main/scala/eq.scala
@@ -0,0 +1,41 @@
+package magnolia.examples
+
+import magnolia._
+import scala.language.experimental.macros
+
+/** typeclass for testing the equality of two values of the same type */
+trait Eq[T] { def equal(value: T, value2: T): Boolean }
+
+/** companion object to [[Eq]] */
+object Eq {
+
+  /** type constructor for the equality typeclass */
+  type Typeclass[T] = Eq[T]
+
+  /** defines equality for this case class in terms of equality for all its parameters */
+  def combine[T](ctx: CaseClass[Eq, T]): Eq[T] = new Eq[T] {
+    def equal(value1: T, value2: T) = ctx.parameters.forall { param =>
+      param.typeclass.equal(param.dereference(value1), param.dereference(value2))
+    }
+  }
+
+  /** choose which equality subtype to defer to
+    *
+    *  Note that in addition to dispatching based on the type of the first parameter to the `equal`
+    *  method, we check that the second parameter is the same type. */
+  def dispatch[T](ctx: SealedTrait[Eq, T]): Eq[T] = new Eq[T] {
+    def equal(value1: T, value2: T): Boolean = ctx.dispatch(value1) {
+      case sub =>
+        sub.cast.isDefinedAt(value2) && sub.typeclass.equal(sub.cast(value1), sub.cast(value2))
+    }
+  }
+
+  /** equality typeclass instance for strings */
+  implicit val string: Eq[String] = new Eq[String] { def equal(v1: String, v2: String) = v1 == v2 }
+
+  /** equality typeclass instance for integers */
+  implicit val int: Eq[Int] = new Eq[Int] { def equal(v1: Int, v2: Int) = v1 == v2 }
+
+  /** binds the Magnolia macro to the `gen` method */
+  implicit def gen[T]: Eq[T] = macro Magnolia.gen[T]
+}
diff --git a/examples/shared/src/main/scala/show.scala b/examples/shared/src/main/scala/show.scala
new file mode 100644
index 0000000..50b34ee
--- /dev/null
+++ b/examples/shared/src/main/scala/show.scala
@@ -0,0 +1,63 @@
+package magnolia.examples
+
+import magnolia._
+import scala.language.experimental.macros
+
+/** shows one type as another, often as a string
+  *
+  *  Note that this is a more general form of `Show` than is usual, as it permits the return type to
+  *  be something other than a string. */
+trait Show[Out, T] { def show(value: T): Out }
+
+trait GenericShow[Out] {
+
+  /** the type constructor for new [[Show]] instances
+    *
+    *  The first parameter is fixed as `String`, and the second parameter varies generically. */
+  type Typeclass[T] = Show[Out, T]
+
+  def join(typeName: String, strings: Seq[String]): Out
+
+  /** creates a new [[Show]] instance by labelling and joining (with `mkString`) the result of
+    *  showing each parameter, and prefixing it with the class name */
+  def combine[T](ctx: CaseClass[Typeclass, T]): Show[Out, T] = new Show[Out, T] {
+    def show(value: T) =
+      if (ctx.isValueClass) {
+        val param = ctx.parameters.head
+        param.typeclass.show(param.dereference(value))
+      } else {
+        val paramStrings = ctx.parameters.map { param =>
+          s"${param.label}=${param.typeclass.show(param.dereference(value))}"
+        }
+
+        join(ctx.typeName.split("\\.").last, paramStrings)
+      }
+  }
+
+  /** choose which typeclass to use based on the subtype of the sealed trait */
+  def dispatch[T](ctx: SealedTrait[Typeclass, T]): Show[Out, T] = new Show[Out, T] {
+    def show(value: T): Out = ctx.dispatch(value) { sub =>
+      sub.typeclass.show(sub.cast(value))
+    }
+  }
+
+  /** bind the Magnolia macro to this derivation object */
+  implicit def gen[T]: Show[Out, T] = macro Magnolia.gen[T]
+}
+
+/** companion object to [[Show]] */
+object Show extends GenericShow[String] {
+
+  /** show typeclass for strings */
+  implicit val string: Show[String, String] = new Show[String, String] {
+    def show(s: String): String = s
+  }
+
+  def join(typeName: String, params: Seq[String]): String =
+    params.mkString(s"$typeName(", ",", ")")
+
+  /** show typeclass for integers */
+  implicit val int: Show[String, Int] = new Show[String, Int] {
+    def show(s: Int): String = s.toString
+  }
+}