one-liner-instances
===================
This package uses machinery from *[one-liner][]* in order to provide default
implementations for methods from `Num`, `Fractional`, `Floating`, `Semigroup`,
and `Monoid`. These will work for any types (deriving `Generic`) that are
made with one constructor, whose fields are all instances of that typeclass.
[one-liner]: https://hackage.haskell.org/package/one-liner
So, `gPlus` (generic addition) will work for:
```haskell
data Tup1 a b = Tup1 a b -- requires Num a, Num b
data Tup2 a = Tup2 Int a -- requires Num a, Num b
data Tup3 = Tup3 Int Double
data Tup4 a b = Tup4 Int Double -- no constraint on a or b
```
But not on:
```haskell
data Tup5 a = Tup2 String a -- String is not an instance of Num
```
These are implemented by applying the operation to every field.
Newtype wrappers
----------------
Similar to `WrappedMonoid` and `WarppedMonad` from *base*, some convenient
newtype wrappers are provided that will give free instances of `Num`, etc. for
appropriate types:
If `a` is a data type (deriving `Generic`) with a single constructor whose
fields all have instances of `Num`, then `GNum a` has a `Num` instance (and
same for `Fractional`, `Floating`, etc.).
If `a` is a data type (deriving `Generic`) with a single constructor whose
fields all have instances of `Semigroup`, then `GMonoid a` has a `Semigroup`
instance (and same for `Monoid`).