Incremental

fumieval/incremental を使うと、任意のデータ型の値の差分が取得できる。

動作確認を行なった incremental のバージョン

Main.hs

code: (hs)

{-# LANGUAGE DataKinds #-}

{-# LANGUAGE FlexibleInstances #-}

{-# LANGUAGE OverloadedLabels #-}

{-# LANGUAGE TypeFamilies #-}

{-# LANGUAGE TypeOperators #-}

module Lib where

import Data.Extensible

import Data.Incremental

type Person = Record

'[ "name" >: String

, "age" >: Int

]

instance Incremental String where

type Delta String = String

diff str1 str2 =

if str1 == str2

then Nothing

else Just ""

alice :: Person

alice = #name @= "Alice"

<: #age @= 10

<: nil

bob :: Person

bob = #name @= "Bob"

<: #age @= 10

<: nil

fakeBob :: Person

fakeBob = #name @= "BoB"

<: #age @= 14

<: nil

example :: IO ()

example = do

print $ diff alice bob

print $ diff alice fakeBob

print $ diff bob fakeBob

print $ diff bob bob

実行例

code: (hs)

ghci> example

Just (WrapDelta {unwrapDelta = Just ""} <: WrapDelta {unwrapDelta = Nothing} <: nil)

Just (WrapDelta {unwrapDelta = Just ""} <: WrapDelta {unwrapDelta = Just 14} <: nil)

Nothing