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Add buniq
to README
It's another perfectly legitimate way to construct an object!
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README.md
50
README.md
@ -52,7 +52,9 @@ example data types:
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{-# LANGUAGE TypeApplications #-}
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module Main where
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import Control.Applicative (Alternative (empty))
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import Control.Lens ((.~), (^.), (&), Const (..), Identity, anyOf)
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import Data.Barbie (ProductB (buniq))
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import Data.Functor.Const (Const (..))
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import Data.Functor.Identity (Identity (..))
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import Data.Generic.HKD
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@ -178,14 +180,24 @@ eg7 = eg6 [1] [] ["Tom", "Tim"]
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-- Triple [1] [] ["Tom","Tim"]
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```
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If you're _still_ not satisfied, check out the
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[`buniq`](https://hackage.haskell.org/package/barbies-1.1.2.1/docs/Data-Barbie.html#v:buniq)
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method hiding in `barbies`:
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```haskell
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eg8 :: HKD Triple []
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eg8 = buniq empty
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-- Triple [] [] []
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```
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### Field Access
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The `field` lens, when given a type-applied field name, allows us to focus on
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fields within a record:
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```haskell
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eg8 :: Last Int
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eg8 = eg0 ^. field @"age"
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eg9 :: Last Int
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eg9 = eg0 ^. field @"age"
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-- Last {getLast = Nothing}
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```
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@ -194,9 +206,9 @@ record (note that these set values will _also_ need to be in our functor of
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choice):
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```haskell
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eg9 :: Partial User
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eg9 = eg0 & field @"name" .~ pure "Evil Tom"
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& field @"likesDogs" .~ pure False
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eg10 :: Partial User
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eg10 = eg0 & field @"name" .~ pure "Evil Tom"
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& field @"likesDogs" .~ pure False
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-- User
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-- { name = Last {getLast = Just "Evil Tom"}
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-- , age = Last {getLast = Nothing}
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@ -208,8 +220,8 @@ This also means, for example, we can check whether a particular value has been
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completed for a given partial type:
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```haskell
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eg10 :: Bool
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eg10 = anyOf (field @"name") (isJust . getLast) eg0
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eg11 :: Bool
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eg11 = anyOf (field @"name") (isJust . getLast) eg0
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-- False
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```
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@ -218,8 +230,8 @@ Finally, thanks to the fact that this library exploits some of the internals of
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doesn't exist in our type:
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```{haskell, ignore}
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eg11 :: Identity ()
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eg11 = eg3 ^. field @"oops"
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eg12 :: Identity ()
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eg12 = eg3 ^. field @"oops"
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-- error:
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-- • The type User does not contain a field named 'oops'.
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```
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@ -230,8 +242,8 @@ Just as with field names, we can use positions when working with non-record
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product types:
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```haskell
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eg12 :: Labels Triple
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eg12 = mempty & position @1 .~ Const "hello"
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eg13 :: Labels Triple
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eg13 = mempty & position @1 .~ Const "hello"
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& position @2 .~ Const "world"
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-- Triple
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-- Const "hello"
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@ -242,8 +254,8 @@ eg12 = mempty & position @1 .~ Const "hello"
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Again, this is a `Lens`, so we can just as easily _set_ values:
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```haskell
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eg13 :: Partial User
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eg13 = eg9 & position @2 .~ pure 25
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eg14 :: Partial User
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eg14 = eg10 & position @2 .~ pure 25
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-- User
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-- { name = Last {getLast = Just "Evil Tom"}
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-- , age = Last {getLast = Just 25}
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@ -255,8 +267,8 @@ Similarly, the internals here come to us courtesy of `generic-lens`, so the
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type errors are a delight:
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```{haskell, ignore}
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eg14 :: Identity ()
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eg14 = deconstruct @Identity triple ^. position @4
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eg15 :: Identity ()
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eg15 = deconstruct @Identity triple ^. position @4
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-- error:
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-- • The type Triple does not contain a field at position 4
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```
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@ -268,8 +280,8 @@ names of the fields into the functor we're using. The `label` value gives us
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this interface:
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```haskell
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eg15 :: Labels User
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eg15 = label
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eg16 :: Labels User
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eg16 = label
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-- User
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-- { name = Const "name"
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-- , age = Const "age"
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@ -284,8 +296,8 @@ can implement functions such as `labelsWhere`, which returns the names of all
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fields whose values satisfy some predicate:
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```haskell
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eg16 :: [String]
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eg16 = labelsWhere (isNothing . getLast) eg9
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eg17 :: [String]
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eg17 = labelsWhere (isNothing . getLast) eg10
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-- ["age"]
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```
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