typeless

Some typeclasses inspired and powered by shapeless

Find[L <: HList, A]

Will allow to find a type A in an HList L, if the type is not present it returns None, otherwise Some[A]

Subset[L <: HList,S <: HList]

Similar to Find, but for a group of elements, if all the elements of the S are present in L it returns Some[S] otherwise None

ListToHList[L, H < HList]

Converts a List[L] to an Option[HList]. The ListToHList implicit class exposes two features.

.toProduct[A]: convert List[L] to an Option[A].

.findByType[B]: find type B within List[L]

  import ListToHList.Ops

  sealed trait A
  case class B() extends A
  case class C() extends A

  case class D(b: B, c: C)
  
  val listA: List[A] = List(B(), C())
  
  listA.toProduct[D] === Some(D(B(), C()))
  
  listA.findByType[B] === Some(B())

Convert[L <: Coproduct, S <: Coproduct]

For Coproducts L and S, Convert takes a value of type L and converts it to type S.

example

  type A = String :+: Double :+: CNil
  type B = Double :+: String :+: List[Int] :+: CNil

  Coproduct[A]("test").convert[B] === Some(Coproduct[B]("test"))

CoproductToHList[C <: Coproduct, L <: HList]

For a Seq of Coproducts C, convert to HList of type L

example

    type A = Int :+: String :+: CNil
    type L = String :: Int :: HNil

    Seq(Coproduct[A](1), Coproduct[A]("a")).toHList[L] === Some("a" :: 1 :: HNil))
    
    case class Foo(i:Int, s:String)
    
    Seq(Coproduct[A](1), Coproduct[A]("a")).toHList[Foo] === Some(Food("a", 1))

SelectFunctions[L <: HList, FF <: HList]

Takes an HList of functions FF and an HList of potential arguments Context. It applies the arguments to the functions for which all the arguments are present. It returns an HList with the results. It will not compile if there is a function that cannot be applied.

example

val functions =
    { (x: String, i: Int, d: Double) => d.toInt * i } ::
      { (x: String, i: Int) => s"$x + $i" } ::
      { (x: String, s: Char, i: Int) => i.toDouble } :: 
      { (x: String, s: Char, i: Int) => s.toInt + i * 2 + x.size } ::
      { (x: String) => x.size } ::
      { (x: Char) => x.toInt } ::
      HNil

SelectFunctions.applyAll(1, hi)(functions) // won't compile
SelectFunctions.applyAll(hi, 'a', 1)(functions) == "hi + 1" :: 1.0 :: 101 :: 2 :: 97 :: HNil

FlattenFunctions[Context <: HList, FFF <: HList]

Takes an HList of HLists of functions and an HList of potential arguments, and uses SelectFunctions[Context, FF] to calculate the resulting HList.

example

 val functions1 =
      { (x: String, i: Int) => (x.size + i) } ::
        { (x: String, s: Char, i: Int) => (s.toInt + i * 2 + x.size) } ::
        HNil
val functions2 =
      { (x: String, s: Char, i: Int) => (s.toInt + i + x.size) } ::
        { (i: Int) => i.toDouble } ::
        HNil

val functions = functions1 ::
      functions2 ::
      HNil

FlattenFunctions.applyAll(1, "a", 'a')(functions) === 2 :: 1.0 :: 99 :: HNil

EqualsIgnoringFields[T]

It compares two cases classes excluding specific field names rather than types.

example:

import typeless.hlist.EqualsIgnoringFields.Ops

sealed trait Monarch

case class Butterflies(
  _id: Long,
  date: Long,
  count: Int
) extends Monarch

case class Dictator(
  _id: Long,
  date: Long,
  count: Int
) extends Monarch

val butterfliesStation1 = Butterflies(
      _id = 1,
      date = 1131,
      count = 3
    )
val butterfliesStation2 = Butterflies(
      _id = 2,
      date = 1131,
      count = 2
    )

// the two objects are the same if we ignore those two fields
assert(butterfliesStation1.equalsIgnoringFields(field => field == '_id || field == 'count)(butterfliesStation2)) 
// the two objects are different if not ignoring `count`
assert(!butterfliesStation1.equalsIgnoringFields(_ == '_id)(butterfliesStation2))
// the two objects are different, period
assert(butterfliesStation1 != butterfliesStation2) 

Getting started

Scala 2.11/2.12

libraryDependencies += "ai.x" %% "typeless" % "0.6.0"