Mouse is a small companion to the Cats functional programming library and the Scala standard library.
The library arose from this Cats issue and is a Typelevel member.
Mouse is published for Scala 2.12, 2.13 and 3.0. For Scala.jvm:
"org.typelevel" %% "mouse" % version
For scala.js 1.x:
"org.typelevel" %%% "mouse" % version
Learn more about Mouse at https://typelevel.org/mouse/.
Mouse includes enrichments for:
- Any
- Boolean
- Double
- F[A] for any F, A
- F[Either[A, B]]
- F[Option[A]]
- F[G[A]]
- F[G[H[A]]]
- F[TupleN]
- Int
- Long
- Map
- Option
- String
- Try
- Tuple
scala> import mouse.all._
import mouse.all._
scala> true.option("Its true!")
res0: Option[String] = Some(Its true!)
scala> def makeEven(i: Int) = (i % 2 == 1).applyIf(i)(_ - 1)
def makeEven(i: Int): Int
scala> val e1: Either[String, Int] = Left("failed")
e1: Either[String,Int] = Left(failed)
scala> true.whenA(e1)
res0: Either[String,Unit] = Left(failed)
scala> false.whenA(e1)
res1: Either[String,Unit] = Right(())
scala> res0.cata(msg => s"Message received: ${msg}", "No message")
res1: String = Message received: Its true!
scala> "1.0".parseFloat
res0: Either[NumberFormatException, Float] = Right(1.0F)
scala> "foo".parseIntValidated
res1: cats.data.Validated[NumberFormatException,Int] = Invalid(java.lang.NumberFormatException: For input string: "foo")
scala> val t1 = scala.util.Try(new java.net.URL("https://www.github.com"))
t1: scala.util.Try[java.net.URL] = Success(https://www.github.com)
scala> t1.cata(msg => s"URL is valid!", error => s"URL is invalid: ${error.getMessage}")
res1: String = URL is valid!
scala> t1.toEither
res2: Either[Throwable,java.net.URL] = Right(https://www.github.com)
scala> val t2 = scala.util.Try(new java.net.URL("https//www.github.com"))
t2: scala.util.Try[java.net.URL] = Failure(java.net.MalformedURLException: no protocol: https//www.github.com)
scala> t2.cata(msg => s"URL is valid!", error => s"URL is invalid: ${error.getMessage}")
res3: String = URL is invalid: no protocol: https//www.github.com
scala> t2.toEither
res4: Either[Throwable,java.net.URL] = Left(java.net.MalformedURLException: no protocol: https//www.github.com)
scala> val intToBytes = 123456789.toByteArray
intToBytes: Array[Byte] = Array(7, 91, -51, 21)
scala> val longToBase64 = 123456789L.toBase64
longToBase64: String = AAAAAAdbzRU
scala> 5.squared
res0: Int = 25
scala> 1.5 |> (_.toInt) |> (_.toString)
res0: String = 1
//lift a partial function into a total function to an Either, when you want to treat unhandled input cases as an error
scala> liftEither[Option[Int]]({case Some(n) => n}, a => s"Unexpected: $a")(Some(6))
res0: Either[String,Int] = Right(6)
scala> val mapped = Map(1 -> 2, 3 -> 4).mapKeys(_ * 2)
mapped: Map[Int,Int] = Map(2 -> 2, 6 -> 4)
scala> val foption = List(Option(1), Option(2), Option(4)).mapIn(_ * 2)
foption: List[Option[Int]] = List(Some(2), Some(4), Some(8))
scala> val feither = List(Either.cond(true, 1, "0")).mapIn(_ * 2)
foption: List[Either[String, Int]] = List(Right(2))
scala> val listOption = List(Option(1), Option(2)).mapNested2(_ * 2)
listOption: List[Option[Int]] = List(Some(2), Some(4))
scala> val listOptionList = List(Option(List(1)), Option(List(2))).mapNested3(_ * 2)
listOptionList: List[Option[List[Int]]] = List(Some(List(2)), Some(List(4)))
scala> val tupleHead = (1, 2, 4, 8).head
tupleHead: Int = 1
scala> val tupleLast = (1, 2, 4, 8).last
tupleHead: Int = 8- Provide enrichments to classes from the Scala standard library that convert to Cats datatypes, or otherwise improve the functional programming experience.
Mouse is maintained by @benhutchison and @danicheg.
Issues and pull requests are welcome. Code contributions should be aligned with the above scope to be included, and include unit tests. See contributing guide for more details.
This project supports the Scala code of conduct and aims that its channels (mailing list, Gitter, github, etc.) to be welcoming environments for everyone.