| import shapeless._ // requires.shapeless | |
| import cats._, implicits._, data.Kleisli // requires.cats | |
| import cats.sequence._ //requires kittens | |
| import cats.effect.IO //requires cats-effect | |
| // ofc, uses "-Ypartial-unification" and kind-projector | |
| case class Result() // replace with the JDBC equivalent | |
| case class DB(val r: Result) { | |
| def nextInt: IO[Int] = ??? //IO(g.nextInt) |
| object Conversions { | |
| import cats._, implicits._, data.ValidatedNel | |
| import mouse._, string._, option._ | |
| import shapeless._, labelled._ | |
| private type Result[A] = ValidatedNel[ParseFailure, A] | |
| case class ParseFailure(error: String) | |
| trait Convert[V] { |
Copyright © 2016-2018 Fantasyland Institute of Learning. All rights reserved.
A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.
val square : Int => Int = x => x * x
| def tsort[A](edges: Traversable[(A, A)]): Iterable[A] = { | |
| @tailrec | |
| def tsort(toPreds: Map[A, Set[A]], done: Iterable[A]): Iterable[A] = { | |
| val (noPreds, hasPreds) = toPreds.partition { _._2.isEmpty } | |
| if (noPreds.isEmpty) { | |
| if (hasPreds.isEmpty) done else sys.error(hasPreds.toString) | |
| } else { | |
| val found = noPreds.map { _._1 } | |
| tsort(hasPreds.mapValues { _ -- found }, done ++ found) | |
| } |