#15 - Attempt to use Generic and HListNthLensAux to generate lenses

core/src/main/scala/monocle/thirdparty/HList.scala

@@ -1,7 +1,7 @@
 package monocle.thirdparty
 
-import monocle.Lens
-import shapeless.HList
+import monocle.{SimpleLens, Iso, Lens}
+import shapeless._
 
 
 object hlist extends HListInstances
@@ -15,4 +15,14 @@ trait HListInstances {
     Lens[HL[A1, HL[A2, T]], HL[A1, HL[New, T]], A2, New](_.tail.head, (l, a) => l.copy(tail = l.tail.copy(head = a)))
 
 
+  def pairToHListIso[A1, A2, B1, B2] =
+    Iso[(A1, A2), (B1, B2), HL[A1, HL[A2, HNil]], HL[B1, HL[B2, HNil]]](t => t._1 :: t._2 :: HNil,
+      hl => hl.head -> hl.tail.head
+    )
+
+  def first[S, A, L <: HList](implicit gen : Generic.Aux[S, L], nth : HListNthLensAux[L, shapeless.nat._0.N, A]) = at(shapeless.nat._0)
+
+  def at[S, A, L <: HList](n : Nat)(implicit gen : Generic.Aux[S, L], nth : HListNthLensAux[L, n.N, A]) =
+    SimpleLens[S, A](s => nth.get(gen.to(s)), (s, a) => gen.from(nth.set(gen.to(s))(a)) )
+
 }

examples/src/main/scala/monocle/HListExample.scala

@@ -1,7 +1,7 @@
 package monocle
 
 import monocle.thirdparty.hlist._
-import shapeless.HNil
+import shapeless._
 
 object HListExample extends App {
 
@@ -13,4 +13,15 @@ object HListExample extends App {
 
   println( _2.get(l) )        // "bla"
 
+  println( pairToHListIso.get((1,"bla")) ) // 1
+  println( (pairToHListIso compose _1[Int, HL[String,HNil], Char]).set((1,"bla"), 'c') )  // ('c', "bla")
+
+
+  case class Person(name : String, age : Int)
+  val julien = Person("Julien", 27)
+
+  println( first.get(julien) )
+
+
+
 }