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Add derive via Generic example, and point to latest docs #331

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Jul 11, 2020
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Add derive via Generic example, and point to latest docs #331

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Add derive via Generic example, and point to latest docs
milesfrain Jul 10, 2020
4508ab0
Clarify `derive` and more details on `Generic`
milesfrain Jul 11, 2020
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21 changes: 16 additions & 5 deletions language/Type-Classes.md
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Expand Up @@ -147,11 +147,22 @@ derive instance ordPerson :: Ord Person
```
Currently, the following type classes can be derived:
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Could you add "by the compiler" here please?


- [Data.Generic.Rep (class Generic)](https://pursuit.purescript.org/packages/purescript-generics-rep/6.0.0/docs/Data.Generic.Rep#t:Generic)
- [Data.Eq (class Eq)](https://pursuit.purescript.org/packages/purescript-prelude/4.1.0/docs/Data.Eq#t:Eq)
- [Data.Ord (class Ord)](https://pursuit.purescript.org/packages/purescript-prelude/4.1.0/docs/Data.Ord#t:Ord)
- [Data.Functor (class Functor)](https://pursuit.purescript.org/packages/purescript-prelude/4.1.0/docs/Data.Functor#t:Functor)
- [Data.Newtype (class Newtype)](https://pursuit.purescript.org/packages/purescript-newtype/3.0.0/docs/Data.Newtype#t:Newtype)
- [Data.Generic.Rep (class Generic)](https://pursuit.purescript.org/packages/purescript-generics-rep/docs/Data.Generic.Rep#t:Generic)
- [Data.Eq (class Eq)](https://pursuit.purescript.org/packages/purescript-prelude/docs/Data.Eq#t:Eq)
- [Data.Ord (class Ord)](https://pursuit.purescript.org/packages/purescript-prelude/docs/Data.Ord#t:Ord)
- [Data.Functor (class Functor)](https://pursuit.purescript.org/packages/purescript-prelude/docs/Data.Functor#t:Functor)
- [Data.Newtype (class Newtype)](https://pursuit.purescript.org/packages/purescript-newtype/docs/Data.Newtype#t:Newtype)

Other type classes may be derived via `Generic`:
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To clarify the different senses in which we are using "derive" here, could you replace this with the following?

Note that derive instance is not the only mechanism for allowing you to avoid writing out boilerplate type class instance code. Many type classes not listed here can be derived through other means, such as via a Generic instance. More information on Generic deriving is available in the generics-rep library documentation.

```purescript
import Data.Generic.Rep (class Generic)
import Data.Generic.Rep.Show (genericShow)

derive instance genericPerson :: Generic Person _

instance showPerson :: Show Person where
show = genericShow
```

## Compiler-Solvable Type Classes

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