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8f20c15Andrzej Rybczak
README.md+18−1
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unifiedsplit
@@ -2,7 +2,7 @@
2
2
3[![Build Status](https://github.com/arybczak/effective/workflows/Haskell-CI/badge.svg?branch=master)](https://github.com/arybczak/effective/actions?query=branch%3Amaster)
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4
5−An effect system based on the [ReaderT design pattern](https://www.fpcomplete.com/blog/2017/06/readert-design-pattern/).
5+A simple, yet powerful extensible effects library.
6
6
7Main features:
7Main features:
8
8
@@ -25,3 +25,20 @@ Main features:
25A `Filesystem` effect with two handlers, one that runs in `IO` and another that
25A `Filesystem` effect with two handlers, one that runs in `IO` and another that
26uses an in-memory virtual file system can be found
26uses an in-memory virtual file system can be found
27[here](https://github.com/arybczak/effective/blob/master/examples/FileSystem.hs).
27[here](https://github.com/arybczak/effective/blob/master/examples/FileSystem.hs).
28+
29+## Resources
30+
31+Resources that inspired the rise of this library and had a lot of impact on its
32+design.
33+
34+Talks:
35+
36+* [Monad Transformer State](https://www.youtube.com/watch?v=KZIN9f9rI34) by Michael Snoyman.
37+
38+* [Effects for Less](https://www.youtube.com/watch?v=0jI-AlWEwYI) by Alexis King.
39+
40+Blog posts:
41+
42+* [ReaderT design pattern](https://www.fpcomplete.com/blog/2017/06/readert-design-pattern/) by Michael Snoyman.
43+
44+* [Exceptions Best Practices](https://www.fpcomplete.com/blog/2016/11/exceptions-best-practices-haskell/) by Michael Snoyman.
effective.cabal+5−3
@@ -7,12 +7,13 @@ license-file: LICENSE
7category: Control
7category: Control
8maintainer: andrzej@rybczak.net
8maintainer: andrzej@rybczak.net
9author: Andrzej Rybczak
9author: Andrzej Rybczak
10−synopsis: An effect system based on the ReaderT design pattern.
10+synopsis: A simple, yet powerful extensible effects library.
11
11
12−description: An effect system based on the ReaderT design pattern, combining
12+description: A simple, yet powerful extensible effects library with seamless
13− advantages of both.
13+ integration with the Haskell ecosystem.
14
14
15extra-source-files: CHANGELOG.md
15extra-source-files: CHANGELOG.md
16+
16tested-with: GHC ==8.0.2 || ==8.2.2 || ==8.4.4 || ==8.6.5 || ==8.8.4 || ==8.10.4
17tested-with: GHC ==8.0.2 || ==8.2.2 || ==8.4.4 || ==8.6.5 || ==8.8.4 || ==8.10.4
17 || ==9.0.1 || ==9.2.0.20210422
18 || ==9.0.1 || ==9.2.0.20210422
18
19
@@ -55,6 +56,7 @@ library
55 import: language
56 import: language
56
57
57 build-depends: base <5
58 build-depends: base <5
59+ , containers
58 , exceptions
60 , exceptions
59 , ghc-prim
61 , ghc-prim
60 , monad-control
62 , monad-control
examples/FileSystem.hs+6−6
@@ -32,14 +32,14 @@ instance Exception FsError
32-- Operations
32-- Operations
33
33
34-- | Read contents of a file.
34-- | Read contents of a file.
35−readFile :: (FileSystem :> es, Error FsError :> es) => FilePath -> String -> Eff es ()
35+readFile :: (FileSystem :> es, Error FsError :> es) => FilePath -> Eff es String
36−readFile path contents = stateEffectM $ \FileSystem{..} -> do
36+readFile path = readerEffectM $ \FileSystem{..} -> _readFile _fs path
37− fs <- _writeFile _fs path contents
38− pure ((), FileSystem { _fs = fs, .. })
39
37
40-- | Write contents to a file.
38-- | Write contents to a file.
41−writeFile :: (FileSystem :> es, Error FsError :> es) => FilePath -> Eff es String
39+writeFile :: (FileSystem :> es, Error FsError :> es) => FilePath -> String -> Eff es ()
42−writeFile path = readerEffectM $ \FileSystem{..} -> _readFile _fs path
40+writeFile path contents = stateEffectM $ \FileSystem{..} -> do
41+ fs <- _writeFile _fs path contents
42+ pure ((), FileSystem { _fs = fs, .. })
43
43
44----------------------------------------
44----------------------------------------
45-- Handlers
45-- Handlers