CoflatMap
Related Docs:
object CoflatMap
| package cats
coflatMap is the dual of flatMap on FlatMap.
coflatMap is the dual of flatMap on FlatMap. It applies
a value in a context to a function that takes a value
in a context and returns a normal value.
Example:
scala> import cats.implicits._ scala> import cats.CoflatMap scala> val fa = Some(3) scala> def f(a: Option[Int]): Int = a match { | case Some(x) => 2 * x | case None => 0 } scala> CoflatMap[Option].coflatMap(fa)(f) res0: Option[Int] = Some(6)
Replaces the A value in F[A] with the supplied value.
Replaces the A value in F[A] with the supplied value.
Example:
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)
coflatten is the dual of flatten on FlatMap.
coflatten is the dual of flatten on FlatMap. Whereas flatten removes
a layer of F, coflatten adds a layer of F
Example:
scala> import cats.implicits._ scala> import cats.CoflatMap scala> val fa = Some(3) fa: Option[Int] = Some(3) scala> CoflatMap[Option].coflatten(fa) res0: Option[Option[Int]] = Some(Some(3))
Alias for map, since map can't be injected as syntax if
the implementing type already had a built-in .map method.
Alias for map, since map can't be injected as syntax if
the implementing type already had a built-in .map method.
Example:
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!)
Tuple the values in fa with the result of applying a function with the value
Tuple the values in fa with the result of applying a function with the value
Example:
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForOption scala> Functor[Option].fproduct(Option(42))(_.toString) res0: Option[(Int, String)] = Some((42,42))
Transform an F[A] into an F[B] by providing a transformation from A
to B and one from B to A.
Transform an F[A] into an F[B] by providing a transformation from A
to B and one from B to A.
Example:
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
Lift a function f to operate on Functors
Lift a function f to operate on Functors
Example:
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)
Tuples the A value in F[A] with the supplied B value, with the B value on the left.
Tuples the A value in F[A] with the supplied B value, with the B value on the left.
Example:
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))
Tuples the A value in F[A] with the supplied B value, with the B value on the right.
Tuples the A value in F[A] with the supplied B value, with the B value on the right.
Example:
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))
Empty the fa of the values, preserving the structure
Empty the fa of the values, preserving the structure
Example:
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForList scala> Functor[List].void(List(1,2,3)) res0: List[Unit] = List((), (), ())
Lifts natural subtyping covariance of covariant Functors.
Lifts natural subtyping covariance of covariant Functors.
NOTE: In certain (perhaps contrived) situations that rely on universal
equality this can result in a ClassCastException, because it is
implemented as a type cast. It could be implemented as map(identity), but
according to the functor laws, that should be equal to fa, and a type
cast is often much more performant.
See this example
of widen creating a ClassCastException.
Example:
scala> import cats.Functor scala> import cats.implicits.catsStdInstancesForOption scala> val s = Some(42) scala> Functor[Option].widen(s) res0: Option[Int] = Some(42)
CoflatMapis the dual ofFlatMap.Must obey the laws in cats.laws.CoflatMapLaws