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SLIDES - INTRO [0:00]

SLIDES - PRODUCTS

EXAMPLE - PRODUCTS (representations.scala)

  • Summon a generic for Employee
  • Summon a generic for IceCream
  • Demonstrate Employee and IceCream Reprs
  • Convert IceCream to Employee

SLIDES - COPRODUCTS

EXAMPLE - COPRODUCTS (representations.scala)

  • Copy and paste Shape code in
  • Summon a generic for Shape
  • Demonstrate Shape Reprs for Rectangle and Circle

SLIDES - WRITING GENERIC CODE [30:00]

EXAMPLE - TYPE CLASS INSTANCES (csv.scala)

  • Ignore Lazy
  • Instances for HNil and ::
  • Instances for CNil and :+:
  • Hand-wave over the dependent types part of Generic:
    • Try to use gen.Repr
    • Correct it to a type refinement

SLIDES - DEPENDENT TYPES [60:00]

EXAMPLE - AUX PATTREN (csv.scala)

  • Correct genericEnc to the Aux pattern

EXAMPLE - IMPLICIT DIVERGENCE AND LAZY (csv.scala)

  • Copy and paste code for Tree
  • Demonstrate "implicit not found"

SLIDES - IMPLICIT DIVERGENCE AND LAZY

EXAMPLE - IMPLICIT DIVERGENCE AND LAZY

  • Add Lazy to instances for ::, :+:, and Generic

SLIDES - LITERAL TYPES

EXAMPLE - LITERAL TYPES (REPL)

  • Create two vars:
    • an Int
    • an instance of 42 (use SIP-23 syntax)
  • Show the types of each
  • Attempt to assign 43 to each

SLIDES - TYPE TAGGING

EXAMPLE - TYPE TAGGING (REPL)

  • Use shapeless.syntax.singleton.->> to create an Int tagged with a String
  • Show the type (V with KeyTag[K, V])
  • Show the FieldType type alias
  • Demonstrate what a labelled HList might look like

EXAMPLE - JSON (json.scala)

  • Write JsonObjectEncoders for HNil, ::, CNil, :+:, and Generic
  • Use Lazy immediately

SLIDES - Putting It All Together

EXAMPLE - Migrations (migrations.scala)

implicit def genericMigration[
  A,
  B,
  ARepr        <: HList,
  BRepr        <: HList,
  CommonFields <: HList,
  AddedFields  <: HList,
  Unaligned    <: HList
](
  implicit
  aGen    : LabelledGeneric.Aux[A, ARepr],
  bGen    : LabelledGeneric.Aux[B, BRepr],
  inter   : Intersection.Aux[ARepr, BRepr, CommonFields],
  diff    : Diff.Aux[BRepr, CommonFields, AddedFields],
  empty   : Empty[AddedFields],
  prepend : Prepend.Aux[AddedFields, CommonFields, Unaligned],
  align   : Align[Unaligned, BRepr]
): Migration[A, B] =
  pure { a =>
    val aRepr     = aGen.to(a)
    val common    = inter(aRepr)
    val added     = empty.value
    val unaligned = prepend(added, common)
    val bRepr     = align(unaligned)
    bGen.from(bRepr)
  }

SLIDES - Summary