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author | Jon Pretty <jon.pretty@propensive.com> | 2017-11-09 09:20:20 +0000 |
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committer | Jon Pretty <jon.pretty@propensive.com> | 2017-11-09 09:20:20 +0000 |
commit | c5c9c4f1432391f6af9202dd89872e5aae92ca58 (patch) | |
tree | c26bf5007c6204b9274993035c6e5cc9b9d4f9aa /examples/src/main/scala/eq.scala | |
parent | 3f23cb5bca4ea8be889b714008a85141fe5e213c (diff) | |
download | magnolia-c5c9c4f1432391f6af9202dd89872e5aae92ca58.tar.gz magnolia-c5c9c4f1432391f6af9202dd89872e5aae92ca58.tar.bz2 magnolia-c5c9c4f1432391f6af9202dd89872e5aae92ca58.zip |
Added Scaladocs
Diffstat (limited to 'examples/src/main/scala/eq.scala')
-rw-r--r-- | examples/src/main/scala/eq.scala | 25 |
1 files changed, 21 insertions, 4 deletions
diff --git a/examples/src/main/scala/eq.scala b/examples/src/main/scala/eq.scala index 408f287..cd257f6 100644 --- a/examples/src/main/scala/eq.scala +++ b/examples/src/main/scala/eq.scala @@ -5,21 +5,38 @@ import scala.language.higherKinds 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)) } + 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.typeclass.equal(sub.cast(value1), sub.cast(value2)) } + 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] } |