[foldr]

Yeah, so it's a less good way of accessing record fields than the one present in 99% of other programming languages. Your own description makes this plain. Let's compare to Javascript:

* I don't need to import a module to make available the syntax for getting and setting fields of an object.

* I can use the same syntax for any object, and don't have to worry about doing a bunch of code generation via a badly-designed metaprogramming hack.

* I don't have to worry about adding prefixes to all my field names.

* The syntax uses familiar operators that I won't have to look up again on hackage if I stop writing Javascript for a few months.

* No-one modifying my code can get "clever" and use one of ~50 obscure and unnecessary operators to save a couple of lines of code.

What bugs me is when Haskell advocates try to use all the additional esoteric features of the lens library as an excuse for this fundamental baseline crappiness.

Haskell really just needs proper support for record types. Then people could use lenses when they actually need lenses (never?). At the moment, they're using lenses because they want something that looks almost like a sane syntax for record updates.

[_fq4v]

Record types are not a solution to the problem lens solves. Lens is a good library and a good concept. If we spent some time on it in programming class, most people would get it. When moving to non-Haskell languages, the lack of proper lenses is something I notice almost immediately.

[foldr]

I know what the lens library does - I write Haskell for my day job.

In practice, the main reason people use it is to work around the deficiencies of Haskell's built-in record system:

>I never built fclabels because I wanted people to use my software (maybe just a bit), but I wanted a nice solution for Haskell’s non-composable record labels.(http://fvisser.nl/post/2013/okt/11/why-i-dont-like-the-lens-...)

The other features of lenses don't strike me as particularly useful. YMMV. I'd also question the quality of the library. It's full of junk like e.g. http://hackage.haskell.org/package/lens-4.17.1/docs/src/Cont..., which is just an invitation to write unreadable code.

[tathougies]

My biggest use case for lenses that I miss in other languages is the ability to interact with all elements of a collection, or elements in deeply nested collections.

For example, if I had a list of records with a field named 'categories' holding a list of objects with a field named 'tags', and I wanted to get all of these names in one list, without nested loops, lens makes it easy 'record ^.. categories . each . tags . each' or I could update them all, etc. It's just so easy to do this kind of data munging with lens that writing fors, whiles, etc in other languages is painful.