added some files

.gitignore

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+/.stack-work
+/stack.yaml.lock

LICENSE

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+Copyright Annwan (c) 2023
+
+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 Annwan 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.

lcalc.cabal

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+name:                lcalc
+version:             0.1.0.0
+-- synopsis:
+-- description:
+homepage: https://git.annnwan.me/annwan/lcal
+license: BSD3
+license-file: LICENSE
+author: Annwan
+maintainer: annwan@annwan.me
+copyright: 2023 Annwan
+build-type: Simple
+cabal-version: >=1.10
+extra-source-files: README.md
+
+
+executable lcalc
+  hs-source-dirs:      src
+  main-is:             Main.hs
+  default-language:    Haskell2010
+  build-depends: base >= 4.7 && < 5
+               , lcalc        
+  ghc-options: -Wall
+               -Wcompat
+               -Widentities
+               -Wincomplete-record-updates
+               -Wincomplete-uni-patterns
+               -Wmissing-export-lists
+               -Wmissing-home-modules
+               -Wpartial-fields
+               -Wredundant-constraints
+
+library
+  hs-source-dirs: src
+  exposed-modules: LCalc.Term
+  build-depends: base >= 4.7 && < 5
+               , text
+  default-language: Haskell2010

src/LCalc/Term.hs

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+{-# LANGUAGE OverloadedStrings #-}
+
+module LCalc.Term where
+
+data Term = Variable String
+          | Abstraction String Term
+          | Application Term Term
+
+instance Show Term where
+  show (Variable name) = name
+  show (Abstraction var term)  = "(λ" ++ var ++ "." ++ show term ++ ")"
+  show (Application t1 t2) = "(" ++ show t1 ++ " " ++ show t2 ++ ")"
+
+  

src/Main.hs

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+module Main (main) where
+
+import LCalc.Term
+
+t :: Term
+t = Abstraction "x" (Application (Variable "x") (Variable "x"))
+
+main :: IO ()
+main = putStrLn $ show t
+  

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: lts-20.8
+
+# 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: ">=2.9"
+#
+# 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