The microlens package

[Tags:bsd3, library]

NOTE: If you're writing an app, you probably want microlens-platform – it has the most features. microlens is intended more for library writers who want a tiny lens library (after all, lenses are pretty useful for everything, not just for updating records!).

This library is an extract from lens (with no dependencies). It's not a toy lenses library, unsuitable for “real world”, but merely a small one. It is compatible with lens, and should have same performance. It also has better documentation.

There's a longer readme on Github. It has a migration guide for lens users, a description of other packages in the family, a discussion of other lens libraries you could use instead, and so on.

Here are some usecases for this library:

However, don't use this library if:

As already mentioned, if you're writing an application which uses lenses more extensively, look at microlens-platform – it combines features of most other microlens packages (microlens-mtl, microlens-th, microlens-ghc).

If you want to export getters or folds and don't mind the contravariant dependency, please consider using microlens-contra.

If you haven't ever used lenses before, read this tutorial. (It's for lens, but it applies to microlens just as well.)

Note that microlens has no dependencies starting from GHC 7.10 (base-4.8). Prior to that, it depends on transformers-0.2 or above.


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Change log
Dependencies base (>=4.5 && <5), transformers (>=0.2) [details]
License BSD3
Author Edward Kmett, Artyom
Maintainer Artyom <>
Stability Unknown
Category Data, Lenses
Home page
Bug tracker
Source repository head: git clone git://
Uploaded Tue Mar 7 13:57:36 UTC 2017 by Artyom
Distributions Arch:, LTSHaskell:, NixOS:, Stackage:, Tumbleweed:
Downloads 2369 total (282 in the last 30 days)
6 []
Status Docs available [build log]
Last success reported on 2017-03-07 [all 1 reports]




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