alvinalexander.com | career | drupal | java | mac | mysql | perl | scala | uml | unix  

Scala example source code file (tcpoly_infer_ticket716.scala)

This example Scala source code file (tcpoly_infer_ticket716.scala) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Scala tags/keywords

a, a=, a=, app, b, b, functor, functor, list, listfunctor, oo, oofunctor, oofunctor, todo

The Scala tcpoly_infer_ticket716.scala source code


trait Functor[F[_]] {
  def fmap[A,B](fun: A=>B, arg:F[A]): F[B]
}
object Functor{
  implicit val ListFunctor: Functor[List] = new Functor[List] {
    def fmap[A, B](f: A => B, arg: List[A]):List[B] = arg map f
  }

  final class OOFunctor[F[_],A](arg:F[A])(implicit ftr: Functor[F]) {
    def fmap[B](fun: A=>B):F[B] = ftr.fmap(fun,arg)
  }

  //breaks if uncommented
  implicit def lifttoOO[F[_],A](arg:F[A])(implicit ftr: Functor[F]) = new OOFunctor[F,A](arg)(ftr)

  //works if uncommented
  //implicit def liftListtoOO[A](arg:List[A]):OOFunctor[List,A] = new OOFunctor[List,A](arg)
}

object GeneralLiftingDemo extends App {
  import Functor._
  val l = List(1,2,3)
  val res = l fmap( 1+) // TODO: should not need explicit call to lifttoOO
  println("OO : " + res )
}

Other Scala examples (source code examples)

Here is a short list of links related to this Scala tcpoly_infer_ticket716.scala source code file:

... this post is sponsored by my books ...

#1 New Release!

FP Best Seller

 

new blog posts

 

Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.

A percentage of advertising revenue from
pages under the /java/jwarehouse URI on this website is
paid back to open source projects.