Switch to using cabal

Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>

.gitignore

@@ -1,3 +1,3 @@
-free-monad-example.cabal
 .stack-work/
+dist-newstyle
 *~

README.md

@@ -1 +1,44 @@
-# free-monad-example
+# Free Monad sample project
+
+Using [Hydra](https://github.com/graninas/Hydra) as a reference for study.
+
+# Library
+
+https://hackage.haskell.org/package/free
+
+# Resources
+
+- [What are free monads](https://stackoverflow.com/questions/13352205/what-are-free-monads)
+- [You could have invented free monads](http://www.haskellforall.com/2012/06/you-could-have-invented-free-monads.html)
+- [Purify code using free monads](http://www.haskellforall.com/2012/07/purify-code-using-free-monads.html)
+- [What does free buy us](https://www.parsonsmatt.org/2017/09/22/what_does_free_buy_us.html)
+- [Random gist](https://gist.github.com/CMCDragonkai/165d9a598b8fb333ea65)
+- [Free Monads](https://www.tweag.io/blog/2018-02-05-free-monads/)
+- [Many roads to free monads](https://www.schoolofhaskell.com/user/dolio/many-roads-to-free-monads)
+- [Hierarchical Free Monads & Software Design in Functional Programming by Alexander Granin](https://www.youtube.com/watch?v=3GKQ4ni2pS0)
+
+# Free Monads Performance
+
+- [Asymptotic Improvement of Computations over Free Monads](https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.143.2323&rep=rep1&type=pdf)
+- [Free Monads for less - Part 1](http://comonad.com/reader/2011/free-monads-for-less/)
+- [Free Monads for less - Part 2](http://comonad.com/reader/2011/free-monads-for-less-2/)
+- [Free Monads for less - Part 3](http://comonad.com/reader/2011/free-monads-for-less-3/)
+- [Kan Extensions](http://comonad.com/reader/2008/kan-extensions/)
+- [The Free and The Furious: And by 'Furious' I mean Codensity](https://www.youtube.com/watch?v=EiIZlX_k89Y)
+- [Effects for less - Great talk, must watch](https://www.youtube.com/watch?v=0jI-AlWEwYI)
+- [Problem Set - The Codensity transformation](http://blog.ezyang.com/2012/01/problem-set-the-codensity-transformation/)
+
+# Fix Point
+
+- [Fix and Recursion](https://en.wikibooks.org/wiki/Haskell/Fix_and_recursion)
+- [The Y Combinator](https://mvanier.livejournal.com/2700.html)
+- [The Y Combinator - Slight Return](https://mvanier.livejournal.com/2897.html)
+- [A series of articles on Recursion schemes](https://blog.sumtypeofway.com/archive.html)
+- [Understanding Algebras](https://www.schoolofhaskell.com/user/bartosz/understanding-algebras)
+
+# Jupyter Notebooks (Includes the one used for Free Monad)
+- [https://gitlab.com/SanchayanMaity/haskell-notebooks](https://gitlab.com/SanchayanMaity/haskell-notebooks)
+
+# youtube Recording of the talk
+
+https://www.youtube.com/watch?v=fhu1UQel5eo

app/Main.hs

@@ -1,6 +1,21 @@
+{-# LANGUAGE OverloadedStrings #-}
+
 module Main where
 
+import Database.PostgreSQL.Simple
+import Data.Text (pack)
 import Lib
 
+dslOperations :: Connection -> DSL ()
+dslOperations conn = do
+  logMsg "Logging from inside the DSL"
+  xs <- runQuery conn "select 2 + 2"
+  logMsg $ pack $ show (xs :: [Only Int])
+
 main :: IO ()
-main = putStrLn "Free monad example"
+main = do
+  putStrLn "Free monad example"
+  conn <- connect defaultConnectInfo {
+    connectDatabase = "postgres"
+  }
+  runDSL $ dslOperations conn

free-monad-example.cabal

@@ -0,0 +1,67 @@
+cabal-version:      1.12
+name:               free-monad-example
+version:            0.1.0.0
+description:
+  Please see the README on GitHub at <https://github.com/sanchayanmaity/free-monad-example#readme>
+
+homepage:           https://github.com/sanchayanmaity/free-monad-example#readme
+bug-reports:        https://github.com/sanchayanmaity/free-monad-example/issues
+author:             Sanchayan Maity
+maintainer:         maitysanchayan@gmail.com
+copyright:          2020 Sanchayan Maity
+license:            BSD3
+license-file:       LICENSE
+build-type:         Simple
+extra-source-files: README.md
+
+source-repository head
+  type:     git
+  location: https://github.com/sanchayanmaity/free-monad-example
+
+library
+  exposed-modules:
+    DB.Interpreter
+    DB.Language
+    Lib
+    Logger.Interpreter
+    Logger.Language
+
+  other-modules:    Paths_free_monad_example
+  hs-source-dirs:   src
+  ghc-options:      -Wall -Wunused-binds
+  build-depends:
+      base               >=4.7 && <5
+    , free
+    , postgresql-simple
+    , text
+
+  default-language: Haskell2010
+
+executable free-monad-example-exe
+  main-is:          Main.hs
+  other-modules:    Paths_free_monad_example
+  hs-source-dirs:   app
+  ghc-options:      -Wall -Wunused-binds -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base                >=4.7 && <5
+    , free
+    , free-monad-example
+    , postgresql-simple
+    , text
+
+  default-language: Haskell2010
+
+test-suite free-monad-example-test
+  type:             exitcode-stdio-1.0
+  main-is:          Spec.hs
+  other-modules:    Paths_free_monad_example
+  hs-source-dirs:   test
+  ghc-options:      -Wall -Wunused-binds -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base                >=4.7 && <5
+    , free
+    , free-monad-example
+    , postgresql-simple
+    , text
+
+  default-language: Haskell2010

hie.yaml

@@ -1,13 +0,0 @@
-cradle:
-  stack:
-    - path: "./src"
-      component: "free-monad-example:lib"
-
-    - path: "./app/Main.hs"
-      component: "free-monad-example:exe:free-monad-example-exe"
-
-    - path: "./app/Paths_free_monad_example.hs"
-      component: "free-monad-example:exe:free-monad-example-exe"
-
-    - path: "./test"
-      component: "free-monad-example:test:free-monad-example-test"

package.yaml

@@ -22,8 +22,6 @@ dependencies:
 - base >= 4.7 && < 5
 - free
 - postgresql-simple
-- servant
-- servant-server
 - text
 
 ghc-options:

src/DB/Interpreter.hs

@@ -0,0 +1,13 @@
+module DB.Interpreter where
+
+import Control.Exception (throwIO)
+import Control.Monad.Free.Church (foldF)
+import Database.PostgreSQL.Simple (Connection, Query)
+import DB.Language
+
+interpretSqlDBMethod :: Connection -> Query -> SqlDBMethodF a -> IO a
+interpretSqlDBMethod conn squery (SqlDBMethod runner next) = next <$> runner conn squery
+interpretSqlDBMethod _ _ (SqlThrowException exception _) = throwIO exception
+
+runDB :: Connection -> Query -> SqlDb a -> IO a
+runDB conn squery = foldF $ interpretSqlDBMethod conn squery

src/DB/Language.hs

@@ -0,0 +1,23 @@
+{-# LANGUAGE GADTs #-}
+
+module DB.Language where
+
+import Control.Exception (Exception)
+import Control.Monad.Free.Church (F, liftF)
+import Database.PostgreSQL.Simple (Connection, FromRow, Query)
+
+data SqlDBMethodF next where
+  SqlDBMethod :: FromRow r => (Connection -> Query -> IO [r]) -> ([r] -> next) -> SqlDBMethodF next
+  SqlThrowException :: Exception e => e -> (a -> next) -> SqlDBMethodF next
+
+instance Functor SqlDBMethodF where
+  fmap f (SqlDBMethod runner next) = SqlDBMethod runner (f . next)
+  fmap f (SqlThrowException exceptionMsg next) = SqlThrowException exceptionMsg (f . next)
+
+type SqlDb = F SqlDBMethodF
+
+sqlDbMethod :: FromRow r => (Connection -> Query -> IO [r]) -> SqlDb [r]
+sqlDbMethod action = liftF $ SqlDBMethod action id
+
+sqlThrowException :: Exception e => e -> SqlDb a
+sqlThrowException exception = liftF $ SqlThrowException exception id

src/Lib.hs

@@ -1,55 +1,15 @@
 {-# LANGUAGE GADTs #-}
-{-# LANGUAGE DataKinds #-}
 {-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE Rank2Types #-}
-{-# LANGUAGE ScopedTypeVariables #-}
 
 module Lib where
 
-import Control.Exception
-import Control.Monad.Free.Church
-import Database.PostgreSQL.Simple
-import Data.Text
-
-data SqlDBMethodF next where
-  SqlDBMethod :: FromRow r => (Connection -> Query -> IO [r]) -> ([r] -> next) -> SqlDBMethodF next
-  SqlThrowException :: Exception e => e -> (a -> next) -> SqlDBMethodF next
-
-instance Functor SqlDBMethodF where
-  fmap f (SqlDBMethod runner next) = SqlDBMethod runner (f . next)
-  fmap f (SqlThrowException exceptionMsg next) = SqlThrowException exceptionMsg (f . next)
-
-type SqlDb = F SqlDBMethodF
-
-sqlDbMethod :: FromRow r => (Connection -> Query -> IO [r]) -> SqlDb [r]
-sqlDbMethod action = liftF $ SqlDBMethod action id
-
-sqlThrowException :: Exception e => e -> SqlDb a
-sqlThrowException exception = liftF $ SqlThrowException exception id
-
-interpretSqlDBMethod :: Connection -> Query -> SqlDBMethodF a -> IO a
-interpretSqlDBMethod conn squery (SqlDBMethod runner next) = next <$> runner conn squery
-interpretSqlDBMethod _ _ (SqlThrowException exception _) = throwIO exception
-
-runDB :: Connection -> Query -> SqlDb a -> IO a
-runDB conn squery = foldF $ interpretSqlDBMethod conn squery
-
-data LoggerMethodF next where
-  LogMessage :: Text -> (() -> next) -> LoggerMethodF next
-
-instance Functor LoggerMethodF where
-  fmap f (LogMessage msg next) = LogMessage msg (f . next)
-
-type Logger = F LoggerMethodF
-
-logMessage :: Text -> Logger ()
-logMessage msg = liftF $ LogMessage msg id
-
-interpretLoggerMethod :: LoggerMethodF a -> IO a
-interpretLoggerMethod (LogMessage msg next) = next <$> print msg
-
-runLogger :: Logger () -> IO ()
-runLogger = foldF interpretLoggerMethod
+import Control.Monad.Free.Church (F, foldF, liftF, MonadFree)
+import Database.PostgreSQL.Simple (Connection, FromRow, Query, query_)
+import Data.Text (Text)
+import DB.Interpreter (runDB)
+import DB.Language (SqlDb, sqlDbMethod)
+import Logger.Interpreter (runLogger)
+import Logger.Language (Logger, logMessage)
 
 data DSLMethod next where
   LogMsg :: Logger () -> (() -> next) -> DSLMethod next
@@ -63,9 +23,9 @@ type DSL = F DSLMethod
 
 interpretDSLMethod :: DSLMethod a -> IO a
 interpretDSLMethod (LogMsg logger next) =
-  fmap next $ runLogger logger
+  next <$> runLogger logger
 interpretDSLMethod (RunQuery conn squery sql next) =
-  fmap next $ runDB conn squery sql
+  next <$> runDB conn squery sql
 
 runDSL :: DSL () -> IO ()
 runDSL = foldF interpretDSLMethod

src/Logger/Interpreter.hs

@@ -0,0 +1,11 @@
+module Logger.Interpreter where
+
+import Control.Monad.Free.Church (foldF)
+import Logger.Language
+
+interpretLoggerMethod :: LoggerMethodF a -> IO a
+interpretLoggerMethod (LogMessage msg next) = next <$> print msg
+
+runLogger :: Logger () -> IO ()
+runLogger = foldF interpretLoggerMethod
+

src/Logger/Language.hs

@@ -0,0 +1,18 @@
+{-# LANGUAGE GADTs #-}
+
+module Logger.Language where
+
+import Control.Monad.Free.Church (F, liftF)
+import Data.Text (Text)
+
+data LoggerMethodF next where
+  LogMessage :: Text -> (() -> next) -> LoggerMethodF next
+
+instance Functor LoggerMethodF where
+  fmap f (LogMessage msg next) = LogMessage msg (f . next)
+
+type Logger = F LoggerMethodF
+
+logMessage :: Text -> Logger ()
+logMessage msg = liftF $ LogMessage msg id
+

stack.yaml

@@ -1,66 +0,0 @@
-# This file was automatically generated by 'stack init'
-#
-# Some commonly used options have been documented as comments in this file.
-# For advanced use and comprehensive documentation of the format, please see:
-# https://docs.haskellstack.org/en/stable/yaml_configuration/
-
-# Resolver to choose a 'specific' stackage snapshot or a compiler version.
-# A snapshot resolver dictates the compiler version and the set of packages
-# to be used for project dependencies. For example:
-#
-# resolver: lts-3.5
-# resolver: nightly-2015-09-21
-# resolver: ghc-7.10.2
-#
-# The location of a snapshot can be provided as a file or url. Stack assumes
-# a snapshot provided as a file might change, whereas a url resource does not.
-#
-# resolver: ./custom-snapshot.yaml
-# resolver: https://example.com/snapshots/2018-01-01.yaml
-resolver: lts-15.15
-
-# User packages to be built.
-# Various formats can be used as shown in the example below.
-#
-# packages:
-# - some-directory
-# - https://example.com/foo/bar/baz-0.0.2.tar.gz
-#   subdirs:
-#   - auto-update
-#   - wai
-packages:
-- .
-# Dependency packages to be pulled from upstream that are not in the resolver.
-# These entries can reference officially published versions as well as
-# forks / in-progress versions pinned to a git hash. For example:
-#
-# extra-deps:
-# - acme-missiles-0.3
-# - git: https://github.com/commercialhaskell/stack.git
-#   commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
-#
-# extra-deps: []
-
-# Override default flag values for local packages and extra-deps
-# flags: {}
-
-# Extra package databases containing global packages
-# extra-package-dbs: []
-
-# Control whether we use the GHC we find on the path
-# system-ghc: true
-#
-# Require a specific version of stack, using version ranges
-# require-stack-version: -any # Default
-# require-stack-version: ">=2.3"
-#
-# Override the architecture used by stack, especially useful on Windows
-# arch: i386
-# arch: x86_64
-#
-# Extra directories used by stack for building
-# extra-include-dirs: [/path/to/dir]
-# extra-lib-dirs: [/path/to/dir]
-#
-# Allow a newer minor version of GHC than the snapshot specifies
-# compiler-check: newer-minor

stack.yaml.lock

@@ -1,12 +0,0 @@
-# This file was autogenerated by Stack.
-# You should not edit this file by hand.
-# For more information, please see the documentation at:
-#   https://docs.haskellstack.org/en/stable/lock_files
-
-packages: []
-snapshots:
-- completed:
-    size: 496112
-    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/15/15.yaml
-    sha256: 86169722ad0056ffc9eacc157ef80ee21d7024f92c0d2961c89ccf432db230a3
-  original: lts-15.15