first commit

.gitignore

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+.stack-work/
+*~

CHANGELOG.md

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+# Changelog for `nl`
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to the
+[Haskell Package Versioning Policy](https://pvp.haskell.org/).
+
+## Unreleased
+
+## 0.1.0.0 - YYYY-MM-DD

LICENSE

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+Copyright 2025 Author name here
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1.  Redistributions of source code must retain the above copyright notice, this
+    list of conditions and the following disclaimer.
+
+2.  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.
+
+3.  Neither the name of the copyright holder nor the names of its 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 HOLDER 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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+# nl

Setup.hs

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+import Distribution.Simple
+main = defaultMain

app/Main.hs

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+module Main (main) where
+
+import Data.Maybe (catMaybes)
+import Lib (PadMode (..), numberAllLines, numberAndIncrNonEmptyLines, numberNonEmptyLines, prettyNumberedLines)
+import System.Environment
+
+data LineNumberOption
+  = ReverseNumbering
+  | SkipEmptyLines
+  | IgnoreEmptyLines
+  | LeftAlign
+  | CenterAlign
+  | Help
+  deriving (Eq)
+
+data Args
+  = Args FilePath [LineNumberOption]
+  | InvalidOptions [String]
+  | NoFilePath
+
+parseLineNumberOption :: String -> Maybe LineNumberOption
+parseLineNumberOption "--help" = Just Help
+parseLineNumberOption "--reverse" = Just ReverseNumbering
+parseLineNumberOption "--skip-empty" = Just SkipEmptyLines
+parseLineNumberOption "--ignore-empty" = Just IgnoreEmptyLines
+parseLineNumberOption "--left-align" = Just LeftAlign
+parseLineNumberOption "--center-align" = Just CenterAlign
+parseLineNumberOption _ = Nothing
+
+parseArguments :: [String] -> Args
+parseArguments xs = case reverse xs of
+  [] -> NoFilePath
+  (filename : options) ->
+    let parsedOptions = map parseLineNumberOption options
+     in if Nothing `elem` parsedOptions
+          then InvalidOptions options
+          else Args filename (catMaybes parsedOptions)
+
+printHelp :: String -> IO ()
+printHelp msg = do
+  putStrLn (msg ++ "\n")
+  progName <- getProgName
+  putStrLn ("Usage: " ++ progName ++ " [--reverse | --left-align | --center-align | --skip-empty | --ignore-empty ] <filename>")
+
+readLines :: FilePath -> IO [String]
+readLines path = do
+  text <- readFile path
+  return (lines text)
+
+main :: IO ()
+main = do
+  rawArgs <- getArgs
+  let args = parseArguments rawArgs
+
+  case args of
+    NoFilePath -> printHelp "Missing filename"
+    InvalidOptions options -> printHelp ("Invalid arguments: " ++ show options)
+    Args _ options | Help `elem` options -> printHelp ""
+    Args filepath options -> do
+      let numberFn
+            | IgnoreEmptyLines `elem` options = numberAndIncrNonEmptyLines
+            | SkipEmptyLines `elem` options = numberNonEmptyLines
+            | otherwise = numberAllLines
+
+      let padMode
+            | LeftAlign `elem` options = PadRight
+            | CenterAlign `elem` options = PadCenter
+            | otherwise = PadLeft
+
+      fileLines <- readLines filepath
+
+      let numbered = numberFn fileLines
+          prettyNumbered = prettyNumberedLines padMode numbered
+          revNumbered = numberFn (reverse fileLines)
+          revPrettyNumbered = reverse $ prettyNumberedLines padMode revNumbered
+
+      mapM_
+        putStrLn
+        ( if ReverseNumbering `elem` options
+            then revPrettyNumbered
+            else prettyNumbered
+        )

nl.cabal

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+cabal-version: 2.2
+
+-- This file has been generated from package.yaml by hpack version 0.37.0.
+--
+-- see: https://github.com/sol/hpack
+
+name:           nl
+version:        0.1.0.0
+description:    Please see the README on GitHub at <https://github.com/githubuser/nl#readme>
+homepage:       https://github.com/githubuser/nl#readme
+bug-reports:    https://github.com/githubuser/nl/issues
+author:         Author name here
+maintainer:     example@example.com
+copyright:      2025 Author name here
+license:        BSD-3-Clause
+license-file:   LICENSE
+build-type:     Simple
+extra-source-files:
+    README.md
+    CHANGELOG.md
+
+source-repository head
+  type: git
+  location: https://github.com/githubuser/nl
+
+library
+  exposed-modules:
+      Exercises
+      Lib
+  other-modules:
+      Paths_nl
+  autogen-modules:
+      Paths_nl
+  hs-source-dirs:
+      src
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints
+  build-depends:
+      base >=4.7 && <5
+  default-language: Haskell2010
+
+executable nl-exe
+  main-is: Main.hs
+  other-modules:
+      Paths_nl
+  autogen-modules:
+      Paths_nl
+  hs-source-dirs:
+      app
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base >=4.7 && <5
+    , nl
+  default-language: Haskell2010
+
+test-suite nl-test
+  type: exitcode-stdio-1.0
+  main-is: Spec.hs
+  other-modules:
+      Paths_nl
+  autogen-modules:
+      Paths_nl
+  hs-source-dirs:
+      test
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base >=4.7 && <5
+    , nl
+  default-language: Haskell2010

package.yaml

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+name:                nl
+version:             0.1.0.0
+github:              "githubuser/nl"
+license:             BSD-3-Clause
+author:              "Author name here"
+maintainer:          "example@example.com"
+copyright:           "2025 Author name here"
+
+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/nl#readme>
+
+dependencies:
+- base >= 4.7 && < 5
+
+ghc-options:
+- -Wall
+- -Wcompat
+- -Widentities
+- -Wincomplete-record-updates
+- -Wincomplete-uni-patterns
+- -Wmissing-export-lists
+- -Wmissing-home-modules
+- -Wpartial-fields
+- -Wredundant-constraints
+
+library:
+  source-dirs: src
+
+executables:
+  nl-exe:
+    main:                Main.hs
+    source-dirs:         app
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - nl
+
+tests:
+  nl-test:
+    main:                Spec.hs
+    source-dirs:         test
+    ghc-options:
+    - -threaded
+    - -rtsopts
+    - -with-rtsopts=-N
+    dependencies:
+    - nl

src/Exercises.hs

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+module Exercises (zip', zip'', zipWith', mapM', mapM_') where
+
+zip' :: [a] -> [b] -> [(a, b)]
+zip' [] _ = []
+zip' _ [] = []
+zip' (x : xs) (y : ys) = (x, y) : zip' xs ys
+
+zipWith' :: (a -> b -> c) -> [a] -> [b] -> [c]
+zipWith' _ [] _ = []
+zipWith' _ _ [] = []
+zipWith' f (x : xs) (y : ys) = f x y : zipWith' f xs ys
+
+zip'' :: [a] -> [b] -> [(a, b)]
+zip'' = zipWith' (,)
+
+mapM' :: (a -> IO b) -> [a] -> IO [b]
+mapM' _ [] = return []
+mapM' f (x : xs) = do
+  b <- f x
+  ys <- mapM' f xs
+  return (b : ys)
+
+mapM_' :: (a -> IO b) -> [a] -> IO ()
+mapM_' _ [] = return ()
+mapM_' f (x : xs) = do
+  _ <- f x
+  mapM_' f xs
+  return ()

src/Lib.hs

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+module Lib
+  ( numberLines,
+    numberAllLines,
+    numberNonEmptyLines,
+    numberAndIncrNonEmptyLines,
+    isEmpty,
+    isNotEmpty,
+    pad,
+    PadMode (..),
+    NumberedLine,
+    NumberedLines,
+    prettyNumberedLines,
+  )
+where
+
+import Data.Char
+import Prelude hiding (lines)
+
+type NumberedLine = (Maybe Int, String)
+
+type NumberedLines = [NumberedLine]
+
+data PadMode = PadLeft | PadRight | PadCenter
+
+numberAllLines :: [String] -> NumberedLines
+numberAllLines = numberLines (const True) (const True)
+
+numberNonEmptyLines :: [String] -> NumberedLines
+numberNonEmptyLines = numberLines (const True) isNotEmpty
+
+numberAndIncrNonEmptyLines :: [String] -> NumberedLines
+numberAndIncrNonEmptyLines = numberLines isNotEmpty isNotEmpty
+
+numberLines :: (String -> Bool) -> (String -> Bool) -> [String] -> NumberedLines
+numberLines shouldIncr shouldNumber lines =
+  let go :: Int -> [String] -> NumberedLines
+      go _ [] = []
+      go counter (x : xs)
+        | shouldIncr x && shouldNumber x = (Just counter, x) : go (counter + 1) xs
+        | shouldIncr x = (Nothing, x) : go (counter + 1) xs
+        | shouldNumber x = (Just counter, x) : go counter xs
+        | otherwise = (Nothing, x) : go counter xs
+   in go 1 lines
+
+prettyNumberedLines :: PadMode -> NumberedLines -> [String]
+prettyNumberedLines mode numberedLines =
+  let (numbers, text) = unzip numberedLines
+      numberStrings = map (maybe "" show) numbers
+      maxLength = maximum $ map length numberStrings
+      paddedNumbers = map (pad mode maxLength) numberStrings
+   in zipWith (\n s -> n ++ " " ++ s) paddedNumbers text
+
+pad :: PadMode -> Int -> String -> String
+pad mode n str =
+  let diff = n - length str
+      padding = replicate diff ' '
+      halfPadding = replicate (diff `div` 2) ' '
+   in case mode of
+        PadLeft -> padding ++ str
+        PadRight -> str ++ padding
+        PadCenter -> halfPadding ++ str ++ halfPadding
+
+isEmpty :: String -> Bool
+isEmpty str =
+  null str || all (\s -> not (isPrint s) || isSeparator s) str
+
+isNotEmpty :: String -> Bool
+isNotEmpty = not . isEmpty

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/configure/yaml/
+
+# 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:
+#
+# snapshot: lts-23.0
+# snapshot: nightly-2024-12-13
+# snapshot: ghc-9.8.4
+#
+# 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.
+#
+# snapshot: ./custom-snapshot.yaml
+# snapshot: https://example.com/snapshots/2024-01-01.yaml
+snapshot: lts-22.43
+
+# 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 snapshot.
+# 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 project 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: ">=3.3"
+#
+# 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

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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/topics/lock_files
+
+packages: []
+snapshots:
+- completed:
+    sha256: 08bd13ce621b41a8f5e51456b38d5b46d7783ce114a50ab604d6bbab0d002146
+    size: 720271
+    url: https://raw.githubusercontent.com/commercialhaskell/stackage-snapshots/master/lts/22/43.yaml
+  original: lts-22.43

test/Spec.hs

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+main :: IO ()
+main = putStrLn "Test suite not yet implemented"