forked from joelburget/data-lens-template
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
0 parents
commit 33d8b09
Showing
3 changed files
with
197 additions
and
0 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,138 @@ | ||
{-# LANGUAGE TemplateHaskell, CPP #-} | ||
|
||
{- | | ||
This module provides an automatic Template Haskell | ||
routine to scour data type definitions and generate | ||
accessor objects for them automatically. | ||
-} | ||
module Data.Lens.Template ( | ||
nameDeriveAccessors, deriveAccessors, | ||
) where | ||
|
||
import Language.Haskell.TH.Syntax | ||
import Control.Monad (liftM, when) | ||
import Data.Maybe (catMaybes) | ||
import Data.List (nub) | ||
import Data.List.HT (viewR) | ||
|
||
import Data.Lens.Common | ||
|
||
-- |@deriveAccessors n@ where @n@ is the name of a data type | ||
-- declared with @data@ looks through all the declared fields | ||
-- of the data type, and for each field ending in an underscore | ||
-- generates an accessor of the same name without the underscore. | ||
-- | ||
-- It is "nameDeriveAccessors" n f where @f@ satisfies | ||
-- | ||
-- > f (s ++ "_") = Just s | ||
-- > f x = Nothing -- otherwise | ||
-- | ||
-- For example, given the data type: | ||
-- | ||
-- > data Score = Score { | ||
-- > p1Score_ :: Int | ||
-- > , p2Score_ :: Int | ||
-- > , rounds :: Int | ||
-- > } | ||
-- | ||
-- @deriveAccessors@ will generate the following objects: | ||
-- | ||
-- > p1Score :: Lens Score Int | ||
-- > p1Score = lens p1Score_ (\x s -> s { p1Score_ = x }) | ||
-- > p2Score :: Lens Score Int | ||
-- > p2Score = lens p2Score_ (\x s -> s { p2Score_ = x }) | ||
-- | ||
-- It is used with Template Haskell syntax like: | ||
-- | ||
-- > $( deriveAccessors ''TypeName ) | ||
-- | ||
-- And will generate accessors when TypeName was declared | ||
-- using @data@ or @newtype@. | ||
deriveAccessors :: Name -> Q [Dec] | ||
deriveAccessors n = nameDeriveAccessors n stripUnderscore | ||
|
||
stripUnderscore :: String -> Maybe String | ||
stripUnderscore s = do | ||
(stem,'_') <- viewR s | ||
return stem | ||
|
||
namedFields :: Con -> [VarStrictType] | ||
namedFields (RecC _ fs) = fs | ||
namedFields (ForallC _ _ c) = namedFields c | ||
namedFields _ = [] | ||
|
||
-- |@nameDeriveAccessors n f@ where @n@ is the name of a data type | ||
-- declared with @data@ and @f@ is a function from names of fields | ||
-- in that data type to the name of the corresponding accessor. If | ||
-- @f@ returns @Nothing@, then no accessor is generated for that | ||
-- field. | ||
nameDeriveAccessors :: Name -> (String -> Maybe String) -> Q [Dec] | ||
nameDeriveAccessors t namer = do | ||
info <- reify t | ||
reified <- case info of | ||
TyConI dec -> return dec | ||
_ -> fail errmsg | ||
(params, cons) <- case reified of | ||
DataD _ _ params cons' _ -> return (params, cons') | ||
NewtypeD _ _ params con' _ -> return (params, [con']) | ||
_ -> fail errmsg | ||
decs <- makeAccs params . nub $ concatMap namedFields cons | ||
when (null decs) $ qReport False nodefmsg | ||
return decs | ||
|
||
where | ||
|
||
errmsg = "Cannot derive accessors for name " ++ show t ++ " because" | ||
++ "\n it is not a type declared with 'data' or 'newtype'" | ||
++ "\n Did you remember to double-tick the type as in" | ||
++ "\n $(deriveAccessors ''TheType)?" | ||
|
||
nodefmsg = "Warning: No accessors generated from the name " ++ show t | ||
++ "\n If you are using deriveAccessors rather than" | ||
++ "\n nameDeriveAccessors, remember accessors are" | ||
++ "\n only generated for fields ending with an underscore" | ||
|
||
makeAccs :: [TyVarBndr] -> [VarStrictType] -> Q [Dec] | ||
makeAccs params vars = | ||
liftM (concat . catMaybes) $ mapM (\ (name,_,ftype) -> makeAccFromName name params ftype) vars | ||
|
||
transformName :: Name -> Maybe Name | ||
transformName (Name occ f) = do | ||
n <- namer (occString occ) | ||
return $ Name (mkOccName n) f | ||
|
||
makeAccFromName :: Name -> [TyVarBndr] -> Type -> Q (Maybe [Dec]) | ||
makeAccFromName name params ftype = | ||
case transformName name of | ||
Nothing -> return Nothing | ||
Just n -> liftM Just $ makeAcc name params ftype n | ||
|
||
-- haddock doesn't grok TH | ||
#ifndef __HADDOCK__ | ||
|
||
makeAcc ::Name -> [TyVarBndr] -> Type -> Name -> Q [Dec] | ||
makeAcc name params ftype accName = do | ||
let params' = map (\x -> case x of (PlainTV n) -> n; (KindedTV n _) -> n) params | ||
let appliedT = foldl AppT (ConT t) (map VarT params') | ||
body <- [| | ||
lens | ||
( $( return $ VarE name ) ) | ||
( \x s -> | ||
$( return $ RecUpdE (VarE 's) [(name, VarE 'x)] ) ) | ||
|] | ||
return | ||
[ SigD accName (ForallT (map PlainTV params') | ||
[] (AppT (AppT (ConT ''Lens) appliedT) ftype)) | ||
, ValD (VarP accName) (NormalB body) [] | ||
] | ||
|
||
#endif | ||
|
||
-- first :: Lens TestData Int | ||
-- first = Lens $ \(TestData x y z) -> store (\x' -> TestData x' y z) x | ||
-- | ||
-- second :: Lens TestData Int | ||
-- second = lens (\(TestData x y z) -> y) (\y' (TestData x y z) -> (TestData x y' z)) | ||
-- | ||
-- third :: Lens TestData String | ||
-- third = Lens $ \(TestData x y z) -> store (\z' -> TestData x y z') z |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,30 @@ | ||
Copyright (c)2011, Joel Burget | ||
|
||
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 Joel Burget 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. |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,29 @@ | ||
Name : data-lens-template | ||
Version : 0.1 | ||
License : BSD3 | ||
License-File : LICENSE | ||
Author : Joel Burget <joelburget@gmail.com> | ||
Maintainer : Joel Burget <joelburget@gmail.com> | ||
Category : Data | ||
Synopsis : Utilities for Data.Lens | ||
Description : Automatically derive a @Lens@ instance for your data type for use with @Data.Lens@. | ||
Build-Type : Simple | ||
Cabal-Version : >= 1.2 | ||
|
||
Library | ||
Build-Depends: | ||
comonad-transformers >= 1.6 | ||
, utility-ht >= 0.0.1 && < 0.1 | ||
, base >= 1.0 && < 5 | ||
, template-haskell >= 2.4 && < 2.6 | ||
|
||
Exposed-Modules: | ||
Data.Lens.Template | ||
|
||
Extensions : CPP, TemplateHaskell | ||
GHC-Options: -Wall | ||
|
||
|
||
Source-repository head | ||
type : git | ||
location: git@github.com:joelburget/data-lens-template.git |