It's not that difficult to do in Scala, which is probably the language that comes most close to a mainstream language that has a typesystem powerful enough to e

It's not that difficult to do in Scala, which is probably the language that comes most close to a mainstream language that has a typesystem powerful enough to express this. There are better languages for expressing this more natural (such as Idris) but in the end, the fallacy seems to lie in your claim that this would be "safe and easy to do with dynamic typing". That's what you think until you find out that your solution works in 99% of the cases, except in some special cases, because the compiler didn't have your back. Examples are the standard sort functions in Java and python, which were bugged for a very long time. Btw, here is the executable code in Scala: https://scalafiddle.io/sf/UrDu12b/1 https://scalafiddle.io/sf/UrDu12b/1 Posting it for reference in case Scalafiddle is down: import shapeless._, ops.function._ def multiMap[InputTypes <: HList, MapF, HListF, MapResult] (inputs: List[InputTypes])(mapF: MapF) (implicit fn: FnToProduct.Aux[MapF, InputTypes => MapResult]) = inputs.map(fn(mapF)) val testList2Elems = List( 3 :: "hi" :: HNil, 5 :: "yes" :: HNil ) multiMap(testList2Elems){ (num: Int, str: String) => s"$num times $str is ${List.fill(num)(str).mkString}" }.foreach(println) val testList3Elems = List( 3 :: "hi" :: 3 :: HNil, 5 :: "yes" :: 2 :: HNil, 2 :: "easy" :: 1 :: HNil ) multiMap(testList3Elems){ (num: Int, str: String, mult: Int) => s"$num * $mult times $str is ${List.fill(num*mult)(str).mkString}" }.foreach(println) // As expected, the compiler has our back and the following does not compile val testListWrongElems = List( 3 :: "hi" :: HNil, 5 :: "yes" :: "ups?" :: HNil ) /* * Whoops, does not compile, list shape not good for multiMap :) * multiMap(testListWrongElems){ (num: Int, str: String) => s"$num times $str is ${List.fill(num)(str).mkString}" }.foreach(println) */ /* * Whoops, does not compile, 2-sequences vs 3 argument function :) * multiMap(testList2Elems){ (num: Int, str: String, mult: Int) => s"$num * $mult times $str is ${List.fill(num*mult)(str).mkString}" }.foreach(println) */