| PackageDescription | NOTE: If you're writing an app, you probably want
<http://hackage.haskell.org/package/microlens-platform microlens-platform> – it
has the most features. <http://hackage.haskell.org/package/microlens 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 <http://hackage.haskell.org/package/lens 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 <https://github.com/monadfix/microlens#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:
* You want to define lenses or traversals in your own library, but don't want
to depend on lens. Having lenses available often make working with a library
more pleasant.
* You just want to be able to use lenses to transform data (or even just use
'over _1' to change the first element of a tuple).
* You are new to lenses and want a small library to play with.
However, don't use this library if:
* You need 'Iso's, 'Prism's, indexed traversals, or actually anything else
which isn't defined here (tho some indexed functions are available elsewhere –
containers and vector provide them for their types, and
<http://hackage.haskell.org/package/ilist ilist> provides indexed functions for
lists).
* You want a library with a clean, understandable implementation (in which case
you're looking for <http://hackage.haskell.org/package/lens-simple
lens-simple>).
As already mentioned, if you're writing an application which uses lenses more
extensively, look at <http://hackage.haskell.org/package/microlens-platform
microlens-platform> – it combines features of most other microlens packages
(<http://hackage.haskell.org/package/microlens-mtl microlens-mtl>,
<http://hackage.haskell.org/package/microlens-th microlens-th>,
<http://hackage.haskell.org/package/microlens-ghc microlens-ghc>).
If you want to export getters or folds and don't mind the
<http://hackage.haskell.org/package/contravariant contravariant> dependency,
please consider using <http://hackage.haskell.org/package/microlens-contra
microlens-contra>.
If you haven't ever used lenses before, read
<http://hackage.haskell.org/package/lens-tutorial/docs/Control-Lens-Tutorial.html
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. |