開発環境
- OS X Mavericks - Apple(OS)
- BBEdit - Bare Bones Software, Inc., Emacs (Text Editor)
- Haskell (純粋関数型プログラミング言語)
- GHC (The Glasgow Haskell Compiler) (処理系)
- The Haskell Platform (インストール方法、モジュール等)
C実践プログラミング 第3版 (Steve Oualline (著)、 望月 康司 (監訳) (翻訳)、谷口 功 (翻訳)、オライリー・ジャパン)のⅡ部(単純なプログラミング)の11章(ビット演算)、11.8(ビットマップグラフィックス)、11.10(プログラミング実習)、実習11-2をHaskellで解いてみる。
その他参考書籍
- プログラミングHaskell (オーム社) Graham Hutton(著) 山本 和彦(翻訳)
- Real World Haskell―実戦で学ぶ関数型言語プログラミング (オライリージャパン) Bryan O'Sullivan John Goerzen Don Stewart(著) 山下 伸夫 伊東 勝利 株式会社タイムインターメディア(翻訳)
実習11-2.
コード(BBEdit)
Sample.hs
{-# OPTIONS -Wall -Werror #-}
import Data.Bits
import Data.Word
main :: IO ()
main = putStr $ makeGraphics $ square 10
canvas :: [[Word8]]
canvas = replicate (div xSize 8) $ replicate ySize 0
square :: Int -> [[Word8]]
square n = foldr mySetBit
canvas
[(x, y) | x <- [0..n - 1], y <- [0..n - 1]]
xSize :: Int
xSize = 40
ySize :: Int
ySize = 60
mySetBit :: (Int, Int) -> [[Word8]] -> [[Word8]]
mySetBit (x, y) graphics =
let a = div x 8
b = graphics !! a
c = take y b ++ ((b !! y) .|. (shiftR 0x80 (mod x 8))):drop (y + 1) b
in take a graphics ++ c:drop (a + 1) graphics
myClearBit :: (Int, Int) -> [[Word8]] -> [[Word8]]
myClearBit (x, y) graphics =
let a = div x 8
b = graphics !! a
c = take y b ++
b !! y .&.
complement ((shiftR 0x80 (mod x 8)) :: Word8):drop (y + 1) b
in take a graphics ++ c:drop (a + 1) graphics
myTestBit :: (Int, Int) -> [[Word8]] -> Bool
myTestBit (x, y) graphics =
graphics !! (div x 8) !! y .&. shiftR 0x80 (mod x 8) > 0
makeGraphics :: [[Word8]] -> String
makeGraphics graphics = unlines $ concatStrings (div xSize 8) $
map (\(y, x) -> (map (\b -> if graphics !! x !! y .&. b /= 0 then
'X'
else
'.')
(takeWhile (>0) $ geometricShift 0x80 1)))
[(y, x) | y <- [0..ySize - 1], x <- [0..(div xSize 8) - 1]]
geometricShift :: (Bits b) => b -> Int -> [b]
geometricShift a r = a:(map (`shiftR`r) $ geometricShift a r)
concatStrings :: Int -> [String] -> [String]
concatStrings _ [] = []
concatStrings n x = concat (take n x):concatStrings n (drop n x)
入出力結果(Terminal, runghc)
$ runghc Sample.hs XXXXXXXXXX.............................. XXXXXXXXXX.............................. XXXXXXXXXX.............................. XXXXXXXXXX.............................. XXXXXXXXXX.............................. XXXXXXXXXX.............................. XXXXXXXXXX.............................. XXXXXXXXXX.............................. XXXXXXXXXX.............................. XXXXXXXXXX.............................. ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ ........................................ $
{-# OPTIONS -Wall -Werror #-}を記述してるから、細かく型を指定(:: Double)しないと警告がいっぱい出た。慣れるまでは{-# OPTIONS -Wall -Werror #-}の記述を消さずに細かく型を指定していくことに。
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