types.

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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"

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- Deriving.On

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derivingvia-extras-0.1.0.0.tar.gz [browse] (Cabal source package)
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Versions [RSS]	0.1.0.0
Change log	CHANGELOG.md
Dependencies	base (>=4 && <5), hashable [details]
License	BSD-3-Clause
Author	Baldur Blöndal
Maintainer	Baldur Blöndal
Category	Deriving, Utils
Bug tracker	https://github.com/Icelandjack/derivingvia-extras/issues
Source repo	head: git clone https://github.com/Icelandjack/derivingvia-extras
Uploaded	by BaldurBlondal at 2022-04-29T00:56:43Z
Distributions	NixOS:0.1.0.0
Downloads	122 total (1 in the last 30 days)
Rating	(no votes yet) [estimated by Bayesian average]
Your Rating	λ λ λ
Status	Docs available [build log] Last success reported on 2022-04-29 [all 1 reports]

Readme for derivingvia-extras-0.1.0.0

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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".

{-# 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

>> alice = User "Alice" 50 0xDEADBEAF
>> bob   = User "Bob"   20 0xDEADBEAF
>>
>> alice == bob
True
>> alice <= bob
True
>> hash alice == hash bob
True