scalaz7

Where is Scalaz Bind.bind implemented?

I am curious where the method scalaz.Bind.bind is implemented? Thanks

trait Bind[F[_]] extends Apply[F] { self =>
  ////

  /** Equivalent to `join(map(fa)(f))`. */
  def bind[A, B](fa: F[A])(f: A => F[B]): F[B]
  ...

I am looking at 7.3.0-SNAPSHOT source.

Solution

  • Bind follows typeclass pattern, and those tend to have multiple implementations for different types that support operations defined by them. That implementations called typeclass instances. Most of the Scalaz typeclass instances for Scala standard library classes reside in scalaz.std package. Examples:

    Bind[List]: listInstances implicit value in scalaz.std.ListInstaces trait, defined in scalaz/std/List.scala. It can be imported via scalaz.std.list object (in the same file) or scalaz.Scalaz object (in scalaz/Scalaz.scala), both of which extend the ListInstances trait.

    Bind[Option]: optionInstances implicit value in sclaaz.std.OptionInstances, defined in scalaz/std/Option.scala. It can be imported via scalaz.std.option object (in the same file) or scalaz.Scalaz object (in scalaz/Scalaz.scala), both of which extend the OptionInstances trait.

    You can also create Scalaz typeclass instances for your own types by creating implicit values or conversions that implement one or more corresponding traits. To be visible, implicits must be imported into your context.