first commit

.gitignore

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+.stack-work/
+*~

ChangeLog.md

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+# Changelog for lambdatest
+
+## Unreleased changes

LICENSE

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+Copyright Author name here (c) 2022
+
+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 Author name here 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.

README.md

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+# lambdatest

Setup.hs

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+import Distribution.Simple
+main = defaultMain

app/Main.hs

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+module Main where
+
+import Lib
+
+main :: IO ()
+main = entrypoint 

lambdatest.cabal

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+cabal-version: 1.12
+
+-- This file has been generated from package.yaml by hpack version 0.34.4.
+--
+-- see: https://github.com/sol/hpack
+
+name:           lambdatest
+version:        0.1.0.0
+description:    Please see the README on GitHub at <https://github.com/githubuser/lambdatest#readme>
+author:         Raphael Jacobs
+maintainer:     raphy@dekedin.me
+copyright:      2022 Raphael Jacobs
+license:        BSD3
+license-file:   LICENSE
+build-type:     Simple
+extra-source-files:
+    README.md
+    ChangeLog.md
+
+library
+  exposed-modules:
+      Lib
+      Parser
+      UntypedLambda
+  other-modules:
+      Paths_lambdatest
+  hs-source-dirs:
+      src
+  build-depends:
+      attoparsec
+    , base >=4.7 && <5
+    , bytestring
+    , cleff
+    , containers
+  default-language: Haskell2010
+
+executable lambdatest-exe
+  main-is: Main.hs
+  other-modules:
+      Paths_lambdatest
+  hs-source-dirs:
+      app
+  default-extensions:
+      OverloadedStrings
+  ghc-options: -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      attoparsec
+    , base >=4.7 && <5
+    , bytestring
+    , cleff
+    , containers
+    , lambdatest
+  default-language: Haskell2010
+
+test-suite lambdatest-test
+  type: exitcode-stdio-1.0
+  main-is: Spec.hs
+  other-modules:
+      Paths_lambdatest
+  hs-source-dirs:
+      test
+  ghc-options: -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      attoparsec
+    , base >=4.7 && <5
+    , bytestring
+    , cleff
+    , containers
+    , lambdatest
+  default-language: Haskell2010

package.yaml

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+name:                lambdatest
+version:             0.1.0.0
+# github:              "githubuser/lambdatest"
+license:             BSD3
+author:              "Raphael Jacobs"
+maintainer:          "raphy@dekedin.me"
+copyright:           "2022 Raphael Jacobs"
+
+extra-source-files:
+- README.md
+- ChangeLog.md
+
+# Metadata used when publishing your package
+# synopsis:            Short description of your package
+# category:            Web
+
+# To avoid duplicated efforts in documentation and dealing with the
+# complications of embedding Haddock markup inside cabal files, it is
+# common to point users to the README.md file.
+description:         Please see the README on GitHub at <https://github.com/githubuser/lambdatest#readme>
+
+dependencies:
+- base >= 4.7 && < 5
+- cleff
+- attoparsec
+- bytestring
+- containers
+
+library:
+  source-dirs: src
+
+executables:
+  lambdatest-exe:
+    main:                Main.hs
+    source-dirs:         app
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - lambdatest
+    default-extensions:
+    - OverloadedStrings
+
+tests:
+  lambdatest-test:
+    main:                Spec.hs
+    source-dirs:         test
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - lambdatest

src/Lib.hs

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+-- {-# LANGUAGE DataKinds, GADTs, TemplateHaskell, TypeOperators #-}
+-- {-# LANGUAGE KindSignatures #-}
+-- {-# LANGUAGE FlexibleContexts #-}
+module Lib
+    ( Identifier(..), Expression(..), -- exported for testing
+      entrypoint
+    ) where
+
+import System.IO
+
+import Parser
+import UntypedLambda
+
+-- import Cleff
+-- import Cleff.Input
+-- import Cleff.Output
+-- import Cleff.State
+-- import Data.Maybe (fromMaybe)
+--
+
+mainloop :: Int -> Expression -> IO ()
+mainloop i expr = do
+  putStrLn $ show i ++ ": " ++ show expr
+  -- _ <- getLine
+  let new = reduce expr 
+  if new == expr 
+    then do 
+      putStrLn "reached normal form. Quitting."
+    else mainloop (i+1) $ reduce expr
+
+entrypoint = do
+
+  setupbuffering 
+
+  putStrLn "Write your lambda expression:\n" 
+  expr <- getLine  
+  case runparse expr of
+    Right ex -> mainloop 0 ex 
+    Left err -> putStrLn $ "Parsing failed! :" ++ err
+
+
+setupbuffering :: IO ()
+setupbuffering = do 
+  hSetBuffering stdin LineBuffering
+  hSetBuffering stdout LineBuffering

src/Parser.hs

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+module Parser where
+
+
+import UntypedLambda
+
+import Data.Attoparsec.ByteString
+import Data.Attoparsec.ByteString.Char8
+
+import qualified Data.ByteString as BS
+import qualified Data.String as BS
+import Control.Applicative ((<|>))
+
+
+expressionparser :: Parser Expression
+expressionparser = choice [applyparser, parensparser, identparser, lambdaparser]
+  -- exp <- choice [parensparser, 
+                 -- identparser, 
+                 -- lambdaparser, 
+                 -- applyparser] 
+  -- endOfInput
+  -- return exp
+
+parensparser :: Parser Expression
+parensparser = do
+  char '('
+  many' space
+  exp <- expressionparser
+  many' space
+  char ')'
+  -- <?>
+  return exp
+
+identparser :: Parser Expression
+identparser = Var . Identifier <$> many1 letter_ascii
+-- identparser = do 
+  -- name <- many1 letter_ascii
+
+lambdaparser :: Parser Expression
+lambdaparser = do
+  char '\\' <|> char 'λ'
+  ids <- sepBy1' (many1 letter_ascii) (many1' space)
+  many' space
+  char '.'
+  many' space
+  Lambda (fmap Identifier ids) <$> expressionparser
+
+
+applyparser :: Parser Expression
+applyparser = do
+  firstexp <- nonrecexpparse
+  many1' space
+  otherexp <- sepBy1' nonrecexpparse (many1' space)
+  return $ leftassoc firstexp otherexp
+  -- Application e1 <$> expressionparser
+    where nonrecexpparse = choice [parensparser, identparser, lambdaparser]
+          leftassoc :: Expression -> [Expression] -> Expression
+          leftassoc x xs = foldl1 Application (x:xs)
+
+
+-- runparse :: String -> Result Expression
+runparse = parseOnly expressionparser . BS.fromString
+

src/UntypedLambda.hs

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+module UntypedLambda where
+
+import qualified Data.Map as M
+
+-- Let's start defining a few wrapper types, togheter with
+-- the definition of our lambda expression and a map-based environment.
+newtype Identifier = Identifier String
+  deriving Eq
+
+instance Show Identifier where
+  show (Identifier s) = s
+
+
+data Expression = Var Identifier
+                | Lambda [Identifier] Expression
+                | Application Expression Expression
+  deriving (Eq)
+
+instance Show Expression where
+  show (Var s) = show s
+  show (Lambda ids ex) = "λ" ++ show ids ++ "." ++ show ex
+  show (Application m n) = enclosem m ++ " " ++ enclosen n
+    where 
+      enclosem k@(Lambda _ _) = enclose $ show k 
+      enclosem x = show x
+      enclosen k@(Lambda _ _) = enclose $ show k 
+      enclosen k@(Application _ _) = enclose $ show k 
+      enclosen x = show x
+      enclose s = "(" ++ s ++ ")"
+    
+
+
+-- name a more iconic duo: eval and apply!
+--
+-- data Lcomp :: Effect where
+--   Reduce :: Expression -> Lcomp m Expression -- also known as EVAL 
+--   Apply :: Expression -> Expression -> Lcomp m Expression
+-- makeEffect ''Lcomp
+--
+-- let's make our first, naive interpreter.
+
+replace :: Identifier -> Expression -> Expression -> Expression
+replace var ex k@(Var p) = if p == var then ex else k
+replace var ex k@(Lambda ids body) = if var `elem` ids then k else Lambda ids (replace var ex body)
+replace var ex k@(Application m n) = Application (replace var ex m) (replace var ex n)
+
+simpleapply :: Expression -> Expression -> Expression
+simpleapply (Lambda [] ex) p = Application ex p -- lambdas with no arguments are constants.
+simpleapply (Lambda [i] ex) p = replace i p ex
+simpleapply (Lambda (i:ids) ex) p = Lambda ids (replace i p ex)
+simpleapply m n = Application m n
+
+
+reduce :: Expression -> Expression
+reduce (Application m n) = simpleapply (reduce m) (reduce n)
+reduce (Lambda ids m) = Lambda ids (reduce m)
+reduce (Var id) = Var id
+
+

stack.yaml

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+# 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:
+  url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/18/25.yaml
+
+# 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:
+  - cleff-0.2.1.0
+  - rec-smallarray-0.1.0.0
+
+# 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: ">=2.7"
+#
+# 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

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+# 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
+
+snapshots:
+- original:
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/18/25.yaml
+  completed:
+    sha256: 1b74fb5e970497b5aefae56703f1bd44aa648bd1a5ef95c1eb8c29775087e2bf
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/18/25.yaml
+    size: 587393
+packages:
+- original:
+    hackage: cleff-0.2.1.0
+  completed:
+    pantry-tree:
+      sha256: 6a3da74b18631cde90e29a371f791003d130c5d8f16f02c7490949d15f9d8c7e
+      size: 2030
+    hackage: cleff-0.2.1.0@sha256:94e50aaf971a071ccf995de9e516daaab7e52de0f4fced0d6bcb7f4f5a9cdba5,5925
+- original:
+    hackage: rec-smallarray-0.1.0.0
+  completed:
+    pantry-tree:
+      sha256: 5b23f667b0dd7c3966b572c12c0d04a502d653ed00adcc5e11467311086ded5a
+      size: 383
+    hackage: rec-smallarray-0.1.0.0@sha256:d79627e8790f2d5a19192e5df790a292237929b9572cecbfbcf3648a77b2e14c,2857

test/Spec.hs

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+{-# LANGUAGE OverloadedStrings #-}
+
+import Parser
+
+import Data.Attoparsec.ByteString
+
+-- GHETTO TESTING TIME!!!!
+
+test :: String -> Bool -> IO ()
+test name cond = if cond
+  then putStrLn $ "Test " ++ name ++ " passed."
+  else putStrLn $ "Test " ++ name ++ " not passed!!"
+
+
+-- force s = case runparse s of
+  -- Fail {} -> "Fail"
+  -- Partial f  -> show $ f ""
+  -- Done _ r   -> show r
+
+
+main :: IO ()
+main = do
+  print $ runparse "(x)"
+  print $ runparse "(   x )"
+  print $ runparse "( 33)"
+  print $ runparse "( (( ( y ))))"
+  print $ runparse "(((p ))"
+
+
+  print $ "testing lambda"
+
+  print $ runparse "\\x.x"
+  print $ runparse "\\x.(x)"
+  print $ runparse "(\\x.y)"
+
+  print $ runparse "\\x y z.x"
+
+  print $ "testing application"
+
+  print $ runparse "x y"
+  print $ runparse "x y z"
+  print $ runparse "(x y) z"
+
+  print $ runparse "\\x.(x x)"
+  print $ runparse "\\x.x x x"
+
+