Functor

abstract def map[A, B](fa: F[A])(f: (A) ⇒ B): F[B]

final def !=(arg0: Any): Boolean

final def ##(): Int

final def ==(arg0: Any): Boolean

def as[A, B](fa: F[A], b: B): F[B]

Replaces the A value in F[A] with the supplied value.

scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForList

scala> Functor[List].as(List(1,2,3), "hello")
res0: List[String] = List(hello, hello, hello)

final def asInstanceOf[T0]: T0

def clone(): AnyRef

def compose[G[_]](implicit arg0: Functor[G]): Functor[[α]F[G[α]]]

def compose[G[_]](implicit arg0: Invariant[G]): Invariant[[α]F[G[α]]]

def composeContravariant[G[_]](implicit arg0: Contravariant[G]): Contravariant[[α]F[G[α]]]

def composeFunctor[G[_]](implicit arg0: Functor[G]): Invariant[[α]F[G[α]]]

final def eq(arg0: AnyRef): Boolean

def equals(arg0: Any): Boolean

def finalize(): Unit

final def fmap[A, B](fa: F[A])(f: (A) ⇒ B): F[B]

Alias for map, since map can't be injected as syntax if the implementing type already had a built-in .map method.

scala> import cats.implicits._

scala> val m: Map[Int, String] = Map(1 -> "hi", 2 -> "there", 3 -> "you")

scala> m.fmap(_ ++ "!")
res0: Map[Int,String] = Map(1 -> hi!, 2 -> there!, 3 -> you!)

def fproduct[A, B](fa: F[A])(f: (A) ⇒ B): F[(A, B)]

Tuple the values in fa with the result of applying a function with the value

scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForOption

scala> Functor[Option].fproduct(Option(42))(_.toString)
res0: Option[(Int, String)] = Some((42,42))

final def getClass(): Class[_]

def hashCode(): Int

def imap[A, B](fa: F[A])(f: (A) ⇒ B)(g: (B) ⇒ A): F[B]

Transform an F[A] into an F[B] by providing a transformation from A to B and one from B to A.

scala> import cats.implicits._
scala> import scala.concurrent.duration._
scala> val durSemigroup: Semigroup[FiniteDuration] =
     | Invariant[Semigroup].imap(Semigroup[Long])(Duration.fromNanos)(_.toNanos)
scala> durSemigroup.combine(2.seconds, 3.seconds)
res1: FiniteDuration = 5 seconds

final def isInstanceOf[T0]: Boolean

def lift[A, B](f: (A) ⇒ B): (F[A]) ⇒ F[B]

Lift a function f to operate on Functors

scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForOption

scala> val o = Option(42)
scala> Functor[Option].lift((x: Int) => x + 10)(o)
res0: Option[Int] = Some(52)

final def ne(arg0: AnyRef): Boolean

final def notify(): Unit

final def notifyAll(): Unit

final def synchronized[T0](arg0: ⇒ T0): T0

def toString(): String

def tupleLeft[A, B](fa: F[A], b: B): F[(B, A)]

Tuples the A value in F[A] with the supplied B value, with the B value on the left.

scala> import scala.collection.immutable.Queue
scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForQueue

scala> Functor[Queue].tupleLeft(Queue("hello", "world"), 42)
res0: scala.collection.immutable.Queue[(Int, String)] = Queue((42,hello), (42,world))

def tupleRight[A, B](fa: F[A], b: B): F[(A, B)]

Tuples the A value in F[A] with the supplied B value, with the B value on the right.

scala> import scala.collection.immutable.Queue
scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForQueue

scala> Functor[Queue].tupleRight(Queue("hello", "world"), 42)
res0: scala.collection.immutable.Queue[(String, Int)] = Queue((hello,42), (world,42))

def void[A](fa: F[A]): F[Unit]

Empty the fa of the values, preserving the structure

scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForList

scala> Functor[List].void(List(1,2,3))
res0: List[Unit] = List((), (), ())

final def wait(): Unit

final def wait(arg0: Long, arg1: Int): Unit

final def wait(arg0: Long): Unit

def widen[A, B >: A](fa: F[A]): F[B]

Lifts natural subtyping covariance of covariant Functors.

scala> import cats.Functor
scala> import cats.implicits.catsStdInstancesForOption

scala> val s = Some(42)
scala> Functor[Option].widen(s)
res0: Option[Int] = Some(42)