derivingvia-extras (empty) → 0.1.0.0

raw patch · 6 files changed

+185/−0 lines, 6 filesdep +basedep +hashablesetup-changed

Dependencies added: base, hashable

Files

• CHANGELOG.md +5/−0
• LICENSE +30/−0
• README.md +39/−0
• Setup.hs +2/−0
• derivingvia-extras.cabal +43/−0
• src/Deriving/On.hs +66/−0

@@ -0,0 +1,5 @@+# Revision history for derivingvia-extras++## 0.1.0.0 -- 2022-04-29++* First version. Added `On` for deriving non-structural instances on a particular record field.

@@ -0,0 +1,30 @@+Copyright (c) 2022, Baldur Blöndal++All rights reserved.++Redistribution and use in source and binary forms, with or without+modification, are permitted provided that the following conditions are met:++    * Redistributions of source code must retain the above copyright+      notice, this list of conditions and the following disclaimer.++    * Redistributions in binary form must reproduce the above+      copyright notice, this list of conditions and the following+      disclaimer in the documentation and/or other materials provided+      with the distribution.++    * Neither the name of Baldur Blöndal nor the names of other+      contributors may be used to endorse or promote products derived+      from this software without specific prior written permission.++THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

@@ -0,0 +1,39 @@+# derivingvia-extras++Miscellaneous via types, for use with `DerivingVia`.++## `On`++The type `On T "field"` derives non-structural instances for `T` by+comparing an evaluting it only at the record field `"field"`.++```haskell+{-# Language DataKinds     #-}+{-# Language DerivingVia   #-}+{-# Language TypeOperators #-}++import Deriving.On+import Data.Hashable++data User = User+  { name   :: String+  , age    :: Int+  , userID :: Integer+  }+  deriving (Eq, Ord, Hashable)+  via User `On` "userID"+```++such that all other fields are ignored++```haskell+>> alice = User "Alice" 50 0xDEADBEAF+>> bob   = User "Bob"   20 0xDEADBEAF+>>+>> alice == bob+True+>> alice <= bob+True+>> hash alice == hash bob+True+```

@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,43 @@+cabal-version: 2.0+name: derivingvia-extras+build-type: Simple+version: 0.1.0.0+license: BSD3+license-file: LICENSE+category: Deriving, Utils+author: Baldur Blöndal+maintainer: Baldur Blöndal+bug-reports: https://github.com/Icelandjack/derivingvia-extras/issues+synopsis: DerivingVia extras - Miscellaneous /via/ types.+extra-source-files:+  CHANGELOG.md+  README.md+description:+    Includes various functionality to use with 'DerivingVia'.+    .+    > -- >> alice = User "Alice" 50 0xDEADBEAF+    > -- >> bob   = User "Bob"   20 0xDEADBEAF+    > -- >>+    > -- >> alice == bob+    > -- True+    > -- >> hash alice == hash bob+    > -- True+    > data User = User+    >   { name   :: String+    >   , age    :: Int+    >   , userID :: Integer+    >   }+    >   deriving (Eq, Ord, Hashable)+    >   via User `On` "userID"++source-repository head+    type: git+    location: https://github.com/Icelandjack/derivingvia-extras++library+    exposed-modules:+        Deriving.On+    hs-source-dirs: src+    default-language: Haskell98+    build-depends:+        base == 4.*, hashable -any

@@ -0,0 +1,66 @@+{-# Language DataKinds                #-}+{-# Language InstanceSigs             #-}+{-# Language ScopedTypeVariables      #-}+{-# Language StandaloneKindSignatures #-}+{-# Language TypeApplications         #-}+{-# Language TypeOperators            #-}+{-# Language UndecidableInstances     #-}++module Deriving.On (On(..)) where++import Data.Function (on)+import Data.Hashable (Hashable(..))+import Data.Kind     (Type)+import Data.Ord      (comparing)+import GHC.Records   (HasField(..))+import GHC.TypeLits  (Symbol)++-- | With 'DerivingVia': to derive non-structural instances. Specifies+-- what field to base instances on.+--+-- The type @'On' User "userID"@ is compared and evaluated based only+-- on the @"userID"@ record field. This uses 'HasField' from+-- @GHC.Records@ to project the relevant component.+--+-- @+-- {-# Language DataKinds     #-}+-- {-# Language DerivingVia   #-}+-- {-# Language TypeOperators #-}+--+-- import Deriving.On+-- import Data.Hashable+--+-- data User = User+--   { name   :: String+--   , age    :: Int+--   , userID :: Integer+--   }+--   deriving (Eq, Ord, Hashable)+--   via User `On` "userID"+-- @+--+-- @+-- >> alice = User "Alice" 50 0xDEADBEAF+-- >> bob   = User "Bob"   20 0xDEADBEAF+-- >>+-- >> alice == bob+-- True+-- >> alice <= bob+-- True+-- >> hash alice == hash bob+-- True+-- @+type    On :: Type -> Symbol -> Type+newtype a `On` field = On a++instance (HasField field a b, Eq b) => Eq (a `On` field) where+  (==) :: a `On` field -> a `On` field -> Bool+  On a1 == On a2 = ((==) `on` getField @field) a1 a2++instance (HasField field a b, Ord b) => Ord (a `On` field) where+  compare :: a `On` field -> a `On` field -> Ordering+  On a1 `compare` On a2 = comparing (getField @field) a1 a2++instance (HasField field a b, Hashable b) => Hashable (a `On` field) where+  hashWithSalt :: Int -> a `On` field -> Int+  hashWithSalt salt (On a) = hashWithSalt salt (getField @field a)