shapeless

I'm chaining transformations, and I'd like to accumulate the result of each transformation so that it can potentially be used in any subsequent step, and also so that all the results are available at the end (mostly for debugging purposes). There are several steps and from time to time I need to add a new step or change the inputs for a step. HList seems to offer a convenient way to collect the results in a flexible but still type-safe way. But I'd rather not complicate the actual steps by making them deal with the HList and the accompanying business. Here's a simplified version of the

Continuing the discussion about converting case classes and Map[String,Any] , I faced some problems when I wanted to use it in a generic way, Here is the main discussion. And when I want to use a generic method like following, compiler complains about the implicits: import MapConvertor._ def convert[A](cc: A)= { cc.toMapRec } Here is the whole code that provides toMapRec : import shapeless._, labelled.FieldType, record._ trait ToMapRec[L <: HList] { def apply(l: L): Map[String, Any] } trait LowPriorityToMapRec { implicit def hconsToMapRec1[K <: Symbol, V, T <: HList](implicit wit: Witness.Aux

Long story short, I'm trying to figure out how to define a function from a generic input to a single-typed output. The background: This is a continuation of Mapping over Shapeless record . After Travis's excellent answer , I now have the following: import shapeless._ import poly._ import syntax.singleton._ import record._ type QueryParams = Map[String, Seq[String]] trait RequestParam[T] { def value: T /** Convert value back to a query parameter representation */ def toQueryParams: Seq[(String, String)] /** Mark this parameter for auto-propagation in new URLs */ def propagate: Boolean protected

I have an HList of strings: val strings = "The Lorax" :: "Dr. Suess" :: HNil I another HList of special types: case class Title(title: String, words: List[String]) case class Author(firstName: String, lastName: String) val book = Title("The Hobbit", List("Hobbit")) :: Author("J.R.R.", "Tolkien") :: HNil I want to turn "strings", my HList of strings, into an HList of mixed types, corresponding to the "book" list. If I have a method to go from a string -> Title, and a method to go from a string -> Author, I feel like this should be very straight forward to essentially get "strings" as an

Apologies for the handwavey title. I’m not entirely sure how to phrase the question succinctly, since I’ve never encountered something like this before. Background info: I have the following trait, where the type U is meant to hold a Shapeless extensible record type: trait Flattened[T] { type U <: shapeless.HList def fields: U } I’m using a blackbox macro (for reasons outside the scope of this question) to create new instances of the trait: object flatten { import scala.language.experimental.macros import scala.reflect.macros.blackbox.Context def apply[T](struct: T): Flattened[T] = macro impl

I have the following trait: trait Storage[C <: Config] { def get(name: String, version: Int): Option[C] def list: List[(String, String)] def register(config: C): Boolean } and I want to create the following class: class MultiStorage[C <: Config](storages: List[Storage[_ <: C]]) extends Storage[C] { def get(name: String, version: Int): Option[C] = {...} def list: List[(String, String)] = {...} def register(config: C) = {...} If not clear, the meaning is that a MultiStorage stores elements of type C (or subtype) in several storages, each of them containing elements of a single type. I am