I am using the lens package and and keep thinking there must be an easy solution to the following problem. Say I have some map (or any At instance) and a lens on its value type, ie aMap :: Map Int...

I am appreciating the Control.Lens package. It really helps with the slightly weak Haskell record syntax. I'm working on some parts of a library where performance is a concern. Does anyone know wha...

I'm trying to figure out the cleanest way to modify values nested inside of Maybe types (or other types for modeling partiality). Here is the example setup: {-# LANGUAGE TemplateHaskell #-} impo...

Possible Duplicate: lenses, fclabels, data-accessor - which library for structure access and mutation is better I'm going to use and learn a Lens package on my next Haskell project. I...

I'm writing a function that does some searching in a sequence of arbitrary symbols. I'd like to make it generic enough so that it works on lists, Foldables as well on ByteStrings and Texts. General...

Really simple question here. After watching an excellent introduction to lenses: http://www.youtube.com/watch?v=efv0SQNde5Q I thought I might attempt one of the simple examples covered in the tal...

I can't seem to find any explanation of what lenses are used for in practical examples. This short paragraph from the Hackage page is the closest I've found: This modules provides a convienient ...

Lenses don't seem to have any disadvantages while having significant advantages over standard Haskell: Is there any reason I shouldn't use lenses wherever possible? Are there performance considerat...

I have an immutable data structure where I have nested values in Maps, like so: case class TradingDay(syms: Map[String, SymDay] = Map.empty) case class SymDay(sym: String, traders: Map[String, Tra...

Could someone explain functional lenses to me? It's a surprisingly difficult subject to google for and I haven't made any progress. All I know is that they provide similar get/set functionality tha...

There are at least three popular libraries for accessing and manipulating fields of records. The ones I know of are: data-accessor, fclabels and lenses. Personally I started with data-accessor an...