
Scala example source code file (Applicative.scala)
The Applicative.scala Scala example source codepackage scalaz //// /** * Applicative Functor, described in [[http://www.soi.city.ac.uk/~ross/papers/Applicative.html Applicative Programming with Effects]] * * Whereas a [[scalaz.Functor]] allows application of a pure function to a value in a context, an Applicative * also allows application of a function in a context to a value in a context (`ap`). * * It follows that a pure function can be applied to arguments in a context. (See `apply2`, `apply3`, ... ) * * Applicative instances come in a few flavours: *  All [[scalaz.Monad]]s are also `Applicative` *  Any [[scalaz.Monoid]] can be treated as an Applicative (see [[scalaz.Monoid]]#applicative) *  Zipping together corresponding elements of Naperian data structures (those of of a fixed, possibly infinite shape) * * @see [[scalaz.Applicative.ApplicativeLaw]] */ //// trait Applicative[F[_]] extends Apply[F] { self => //// def point[A](a: => A): F[A] // alias for point final def pure[A](a: => A): F[A] = point(a) // derived functions override def map[A, B](fa: F[A])(f: A => B): F[B] = ap(fa)(point(f)) override def apply2[A, B, C](fa: => F[A], fb: => F[B])(f: (A, B) => C): F[C] = ap2(fa, fb)(point(f)) // impls of sequence, traverse, etc def traverse[A, G[_], B](value: G[A])(f: A => F[B])(implicit G: Traverse[G]): F[G[B]] = G.traverse(value)(f)(this) def sequence[A, G[_]: Traverse](as: G[F[A]]): F[G[A]] = traverse(as)(a => a) import std.list._ /** Performs the action `n` times, returning the list of results. */ def replicateM[A](n: Int, fa: F[A]): F[List[A]] = listInstance.sequence(List.fill(n)(fa))(this) /** Performs the action `n` times, returning nothing. */ def replicateM_[A](n: Int, fa: F[A]): F[Unit] = listInstance.sequence_(List.fill(n)(fa))(this) /** Filter `l` according to an applicative predicate. */ def filterM[A](l: List[A])(f: A => F[Boolean]): F[List[A]] = l match { case Nil => point(List()) case h :: t => ap(filterM(t)(f))(map(f(h))(b => t => if (b) h :: t else t)) } /** * Returns the given argument if `cond` is `false`, otherwise, unit lifted into F. */ def unlessM[A](cond: Boolean)(f: => F[A]): F[Unit] = if (cond) point(()) else void(f) /** * Returns the given argument if `cond` is `true`, otherwise, unit lifted into F. */ def whenM[A](cond: Boolean)(f: => F[A]): F[Unit] = if (cond) void(f) else point(()) /**The composition of Applicatives `F` and `G`, `[x]F[G[x]]`, is an Applicative */ def compose[G[_]](implicit G0: Applicative[G]): Applicative[λ[α => F[G[α]]]] = new CompositionApplicative[F, G] { implicit def F = self implicit def G = G0 } /**The product of Applicatives `F` and `G`, `[x](F[x], G[x]])`, is an Applicative */ def product[G[_]](implicit G0: Applicative[G]): Applicative[λ[α => (F[α], G[α])]] = new ProductApplicative[F, G] { implicit def F = self implicit def G = G0 } /** An `Applicative` for `F` in which effects happen in the opposite order. */ override def flip: Applicative[F] = new Applicative[F] with FlippedApply { def point[A](a: => A) = Applicative.this.point(a) } trait ApplicativeLaw extends ApplyLaw { /** `point(identity)` is a noop. */ def identityAp[A](fa: F[A])(implicit FA: Equal[F[A]]): Boolean = FA.equal(ap(fa)(point((a: A) => a)), fa) /** `point` distributes over function applications. */ def homomorphism[A, B](ab: A => B, a: A)(implicit FB: Equal[F[B]]): Boolean = FB.equal(ap(point(a))(point(ab)), point(ab(a))) /** `point` is a left and right identity, Fwise. */ def interchange[A, B](f: F[A => B], a: A)(implicit FB: Equal[F[B]]): Boolean = FB.equal(ap(point(a))(f), ap(f)(point((f: A => B) => f(a)))) /** `map` is like the one derived from `point` and `ap`. */ def mapLikeDerived[A, B](f: A => B, fa: F[A])(implicit FB: Equal[F[B]]): Boolean = FB.equal(map(fa)(f), ap(fa)(point(f))) } def applicativeLaw = new ApplicativeLaw {} //// val applicativeSyntax = new scalaz.syntax.ApplicativeSyntax[F] { def F = Applicative.this } } object Applicative { @inline def apply[F[_]](implicit F: Applicative[F]): Applicative[F] = F //// implicit def monoidApplicative[M:Monoid]: Applicative[λ[α => M]] = Monoid[M].applicative //// } Other Scala examples (source code examples)Here is a short list of links related to this Scala Applicative.scala source code file: 
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