(implicit m: Munger[D])
• mungeData(“foo”) // Compiler finds a
Munger[String]](https://image.slidesharecdn.com/scalaimplicits-100316192627-phpapp01/85/Scala-implicits-17-320.jpg)
![Parameters
• Higher kinds!
• def mungeData[M[_], D](d: D)(implicit m:
Munger[D], each: Each[M]) = ...
• mungeData(List(1,2,3))
• Munger[Int]
• Each[List]](https://image.slidesharecdn.com/scalaimplicits-100316192627-phpapp01/85/Scala-implicits-18-320.jpg)
![Implicit Search Scope
// COMPANION OBJECTS
trait Monoid[T]
object Monoid { // SAME NAME
implicit val s = new Monoid[String]
}
// `s` will be available anywhere a
Monoid[String] is needed. Without imports.](https://image.slidesharecdn.com/scalaimplicits-100316192627-phpapp01/85/Scala-implicits-23-320.jpg)
(implicit m: Monoid[T]) = {
// m is available for any implicit
parameters needed within this method
body
}](https://image.slidesharecdn.com/scalaimplicits-100316192627-phpapp01/85/Scala-implicits-24-320.jpg)
Scala implicits
- 1. Implicits 2 Features, 1 Keyword Nick Partridge @nkpart
- 2. 2 Features • Implicit Conversions • Implicit Parameters
- 3. Conversions • int a = 5.3f; // Implicit conversion
- 4. Conversions • val a: A = ...; • val b: B = a; // Compile Fail. Of course.
- 5. Conversions • val a: A = ...; • implicit def (a: A): B = ...; • val b: B = a; • // Profit.
- 6. Conversions Compiler searches the ‘implicit scope’ • val b: B = a; • val b: B = bToA(a);
- 7. Pimp My Library Live Demo.
- 8. Conversions • Also triggered by a method search case class Foo(s: String) { def pl = s + “es” }
- 9. Conversions implicit def toFoo(s: String) = Foo(s) “peach”.pl // == “peaches” toFoo(s).pl
- 10. Not Transitive Implicit A => B Implicit B => C Does not mean Implicit A => C
- 11. View Bounds Live coding!
- 12. The End. Of Part 1.
- 13. Parameters
- 14. Parameters • Scala functions have parameter groups • def foo(a: Int)(b: Int)(c: Int) = ... • foo(1)(2)(3)
- 15. Parameters • The *last* group can be `implicit`. • def mungeData(d: Data)(implicit m: Munger) • mungeData(myData)(myMunger)
- 16. Parameters • implicit val myMunger = new Munger • mungeData(myData)(myMunger) Compiler figures out the last group
- 17. Parameters • def mungeData[D](d: D)(implicit m: Munger[D]) • mungeData(“foo”) // Compiler finds a Munger[String]
- 18. Parameters • Higher kinds! • def mungeData[M[_], D](d: D)(implicit m: Munger[D], each: Each[M]) = ... • mungeData(List(1,2,3)) • Munger[Int] • Each[List]
- 21. Where to get the ‘implicits’ from?
- 22. Implicit Search Scope • Similar to value resolution scope • local variables, values in current object, super classes. • Imported object members • Function parameters
- 23. Implicit Search Scope // COMPANION OBJECTS trait Monoid[T] object Monoid { // SAME NAME implicit val s = new Monoid[String] } // `s` will be available anywhere a Monoid[String] is needed. Without imports.
- 24. Implicit Search Scope def foo[T](t: T)(implicit m: Monoid[T]) = { // m is available for any implicit parameters needed within this method body }
- 25. More! • Anonymous functions • implicit r => { ... } • Import instances • case class Z(a: A) { implicit ia = a } • val z = new Z(someA) • import z._
- 27. La fin.