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Haskell - 実践Haskell - Haskellでの効率的でステートフルの配列 - UArrayを使ってて効率のよう配列を作成する - リストをUArrayに変換

入門Haskellプログラミング (Will Kurt(著)、株式会社クイープ(監修、翻訳)、翔泳社)の UNIT 7(実践Haskell)、LESSON 42(Haskellでの効率的でステートフルの配列)、42.4(バブルソートを実装する)、クイックチェック 42-4の解答を求めてみる。

軽量マークアップ言語

st-lesson/package.yaml

name:                st-lesson
version:             0.1.0.0
github:              "githubuser/st-lesson"
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/st-lesson#readme>

dependencies:
- base >= 4.7 && < 5
- array

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:
  st-lesson-exe:
    main:                Main.hs
    source-dirs:         app
    ghc-options:
    - -threaded
    - -rtsopts
    - -with-rtsopts=-N
    dependencies:
    - st-lesson

tests:
  st-lesson-test:
    main:                Spec.hs
    source-dirs:         test
    ghc-options:
    - -threaded
    - -rtsopts
    - -with-rtsopts=-N
    dependencies:
    - st-lesson

コード

st-lesson/app/Main.hs

module Main (main) where

-- import Lib

import Control.Monad
import Data.Array.ST
import Data.Array.Unboxed

listToUArray :: [Int] -> UArray Int Int
listToUArray vals = runSTUArray $ do
  let end = length vals - 1
  myArray <- newArray (0, end) 0
  forM_ [0 .. end] $ \i -> do
    let val = vals !! i
    writeArray myArray i val
  return myArray

myData :: UArray Int Int
myData = listToUArray [7, 6, 4, 8, 10, 2]

main :: IO ()
main = do
  print myData

入出力結果(Terminal, Zsh)

% stack run
st-lesson-0.1.0.0: unregistering (local file changes: app/Main.hs)
st-lesson> build (lib + exe) with ghc-9.8.4
Preprocessing library for st-lesson-0.1.0.0..
Building library for st-lesson-0.1.0.0..
Preprocessing executable 'st-lesson-exe' for st-lesson-0.1.0.0..
Building executable 'st-lesson-exe' for st-lesson-0.1.0.0..
[1 of 2] Compiling Main [Source file changed]
[3 of 3] Linking .stack-work/dist/aarch64-osx/ghc-9.8.4/build/st-lesson-exe/st-lesson-exe [Objects changed]
ld: warning: -U option is redundant when using -undefined dynamic_lookup
st-lesson> copy/register
Installing library in /Users/.../st-lesson/.stack-work/install/aarch64-osx/27e00dd04a6f7fc061662d4eebb16cc69859af4840b4ab18e626ce23aacafb60/9.8.4/lib/aarch64-osx-ghc-9.8.4/st-lesson-0.1.0.0-3lZxzIFyVubJ5mxkniV0U9
Installing executable st-lesson-exe in /Users/.../st-lesson/.stack-work/install/aarch64-osx/27e00dd04a6f7fc061662d4eebb16cc69859af4840b4ab18e626ce23aacafb60/9.8.4/bin
Registering library for st-lesson-0.1.0.0..
array (0,5) [(0,7),(1,6),(2,4),(3,8),(4,10),(5,2)]
%