I have the following Scala problem: Write a function that will take a list of HLists List(23 :: “a” :: 1.0d :: HNil, 24 :: “b” :: 2.0d :: HNil) # this is list of hlists and return back HList of...

Thanks to https://github.com/milessabin/shapeless/wiki/Feature-overview:-shapeless-2.0.0 I understand how to zip shapeless HLists: Import some stuff from Shapeless 2.0.0-M1: import shapeless._ im...

How can I pass some HList as an argument? So I can make in a such way: def HFunc[F, S, T](hlist: F :: S :: T :: HNil) { // here is some code } HFunc(HList(1, true, "String")) // it works perfect...

Question Is it somehow possible to create an extractor for shapeless' HList that looks like the following. val a ~ _ ~ b = 4 :: "so" :: 4.5 :: HNil => a == 4 && b == 4.5 Repl...

I'm working on a small library for economic models that check the Units of the entities, using Types, e.g. instead of val apples = 2.0 we write val apples = GoodsAmount[KG, Apples](2.0). For creati...

Suppose we have a following definition of HList: data HL spec where HLNil :: HL () HLCons :: h -> HL t -> HL (h, t) Is it possible to somehow enforce a shared constraint on its items? A...

I'm working on an HList implementation and I'm stuck trying to implement a map function for it. I've tried a lot of different approaches but with each one I reach compiler errors related to that fu...

I have tried map show . mapMaybe fromDynamic $ [toDyn "one", toDyn (\x -> x::Integer), toDyn 3, toDyn ()] but it returned ["()"]

I'm using shapeless in Scala, and I'd like to write a function allPairs that will take two HLists and return an HList of all pairs of elements. For example: import shapeless._ val list1 = 1 :: "on...

With recent posts about HaskellDB, I've been motivated to look into HList again. As we now have -XDataKinds in GHC, which actually has an example of heterogeneous lists, I wanted to investigate how...

I've been trying to use HList to create records. I've been using the operators defined in HList-GHCSyntax. It so far works quite nicely, allowing me to write things like this: myRecord = (para...

Is it possible to do a foldLeft on a list of arguments, where the initial value supplied to the fold is a fully curried function, the operator is apply, and the list is a list of arguments to be pa...

sealed abstract trait HList case class :+:[H, T <: HList](head: H, tail: T) extends HList { def :+:[T](v: T) = new :+:(v, this) } case object HNil extends HList { def :+:[T](v: T) = new :+:(...