unbound-generics-0.1.2: README.md

# unbound-generics

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This is a reimplementation of (parts of) [unbound](http://hackage.haskell.org/package/unbound) but using [GHC generics](http://www.haskell.org/ghc/docs/latest/html/libraries/base-4.7.0.1/GHC-Generics.html) instead of [RepLib](https://hackage.haskell.org/package/RepLib).

## Differences from `unbound`

For the most part, I tried to keep the same methods with the same signatures.  However there are a few differences.

1. `fv :: Alpha t => Fold t (Name n)`

   The `fv` method returns a `Fold` (in the sense of the [lens](http://hackage.haskell.org/package/lens) library),
   rather than an `Unbound.Util.Collection` instance.  That means you will generally have to write `toListOf fv t` or some    other summary operation.

2. `isPat :: Alpha t => t -> DisjointSet AnyName`

   You should only notice this if you're implementing an instance of `Alpha` by hand (rather than by using the default
   generic instance).  The original `unbound` returned a `Maybe [AnyName]` here with the same interpretation as `DisjointSet`: `Nothing` means an inconsistency was encountered, or `Just` the free variables of the pattern.

3. `embed :: IsEmbed e => Embedded e -> e` and `unembed :: IsEmbed e => e -> Embedded e`

    The typeclass `IsEmbed` has an `Iso` (again in the sense of the `lens` library) as a method instead of the above pair of methods.

    Again, you should only notice this if you're implementing your own types that are instances of `IsEmbed`.  The easiest thing to do is to use implement `embedded = iso yourEmbed yourUnembed` where `iso` comes from `lens`.  (Although you can also implement it in terms of `dimap` if you don't want to depend on lens)