data-compat (empty) → 0.1.0.0

raw patch · 5 files changed

+118/−0 lines, 5 filesdep +basedep +constraintssetup-changed

Dependencies added: base, constraints

Files

• CHANGELOG.md +5/−0
• LICENSE +20/−0
• Setup.hs +2/−0
• data-compat.cabal +23/−0
• src/Data/Compat.hs +68/−0

@@ -0,0 +1,5 @@+# Revision history for data-compat++## 0.1.0.0 -- 2019-04-23++* First version. Released on an unsuspecting world.

@@ -0,0 +1,20 @@+Copyright (c) 2019 Travis Whitaker++Permission is hereby granted, free of charge, to any person obtaining+a copy of this software and associated documentation files (the+"Software"), to deal in the Software without restriction, including+without limitation the rights to use, copy, modify, merge, publish,+distribute, sublicense, and/or sell copies of the Software, and to+permit persons to whom the Software is furnished to do so, subject to+the following conditions:++The above copyright notice and this permission notice shall be included+in all copies or substantial portions of the Software.++THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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

@@ -0,0 +1,23 @@+cabal-version:       2.2+name:                data-compat+version:             0.1.0.0+synopsis:            Define Backwards Compatibility Schemes for Arbitrary Data+description:         Define Backwards Compatibility Schemes for Arbitrary Data+homepage:            https://github.com/TravisWhitaker/data-compat+bug-reports:         https://github.com/TravisWhitaker/data-compat/issues+license:             MIT+license-file:        LICENSE+author:              Travis Whitaker+maintainer:          pi.boy.travis@gmail.com+copyright:           Travis Whitaker 2019+category:            Data+extra-source-files:  CHANGELOG.md++library+  exposed-modules:     Data.Compat+  -- other-modules:+  -- other-extensions:+  build-depends:       base ^>=4.12.0.0+                     , constraints ^>= 0.10+  hs-source-dirs:      src+  default-language:    Haskell2010

@@ -0,0 +1,68 @@+{-|+Module      : Data.Compat+Description : Backwards Compatibility Schemes for Arbitrary Data+Copyright   : Travis Whitaker 2019+License     : MIT+Maintainer  : pi.boy.travis@gmail.com+Stability   : Provisional+Portability : Portable++See <http://programmable.computer/compatible.html> for a full exposition and+worked examples.+-}++{-# LANGUAGE ConstraintKinds+           , FlexibleContexts+           , KindSignatures+           , RankNTypes+           , ScopedTypeVariables+           , TypeFamilies+           , TypeApplications+           #-}++module Data.Compat where++import Control.Applicative++import Data.Constraint++import Data.Proxy++-- | A class for backwards-compatible data.+class Compat a where+    -- | The predecessor for this type, i.e. the type for the data schema+    --   directly preceeding 'a'.+    type Pred a             :: *+    -- | Any additional constraints required to yield data values. Typically+    --   this will be a class that provides a parser.+    type CompatConstraint a :: * -> Constraint+    -- | A type for wrapping migration results. It is most useful if this type+    --   has `Alternative` and `Monad` instances, enabling the use of+    --   `getCompatible`. `Maybe` is a good first choice.+    type CompatF a          :: * -> *+    -- | How to migrate from a value of the preceeding schema to the current+    --   schema.+    migrate  :: Pred a -> (CompatF a) a+    continue :: Proxy a+             -> Maybe (Dict ( Compat (Pred a)+                            , (CompatConstraint a) (Pred a)+                            , CompatConstraint a ~ CompatConstraint (Pred a)+                            , CompatF a ~ CompatF (Pred a)+                            )+                      )++-- | Recursively migrate a data value to the most recent schema, if possible.+getCompatible+    :: forall a.+       ( Compat a+       , (CompatConstraint a) a+       , Alternative (CompatF a)+       , Monad (CompatF a)+       )+    => (forall c. (Compat c, (CompatConstraint a) c) => (CompatF a) c)+    -> (CompatF a) a+getCompatible f =+    let f' = case continue (Proxy :: Proxy a) of+                Nothing   -> empty+                Just Dict -> getCompatible f >>= migrate+    in f <|> f'