超簡易整形フィルタ

超簡易な欧文整形フィルタ

欧文プレーンテキストを弄っていると、こういうのが便利な時もあるので、備忘録として。

標準入力から受け取って整形された欧文テキストを返す（一行辺りの字数はコマンドライン引数で指定する）。日本語には対応していないが、分かち書きしない和文にはそもそも不要。

$ cat my.txt | format 40

みたいに使う。Textパッケージも使っていないやる気のないコードだが、そもそもそんな大量のテキストを処理することを想定していないのでこのまま。

Format.hs

import Control.Monad
import System.Environment (getArgs)
import System.Exit (exitSuccess)

-- 各行の右端はとりあえず指定字数まで空白で埋める
pretty :: Int -> [String] -> [String] -> Int -> IO ()
pretty count buffer strs n
  | null strs && null buffer = return () 
  | null strs   = flushWithWS 1 >> putStrLn (ws (n-count-(wc-1)*1)) -- 最終行は単純に左揃え
  | expect >  n = flushWithWS p >> putStrLn (ws (n-count-(wc-1)*p)) >> pretty 0 [] strs n
  | expect == n = flushWithWS 1 >> putStrLn (ws 1 ++ s)             >> pretty 0 [] ss n
  | expect <  n = pretty (count + length s) (s:buffer) ss n
  where
    (s:ss) = strs -- 目下読んでいる単語と残りの単語リスト
    wc = length buffer -- バッファの単語数
    expect = count + wc + length s -- 現在行に次の単語を入れると必要になる最低字数
    ws n = take n $ repeat ' ' -- n文字の空白
    p = div (n - count) wc -- 空白を均等割にするときの空白幅
    flushWithWS n = putStr $ drop n $ concatMap (ws n ++) $ reverse $ buffer -- n個の空白を挟みつつバッファを出力


main = do
  args <- map read <$> getArgs
  when (null args) $  putStrLn "Usage: cat file | format (number of letters per line)" >> exitSuccess
  dat <- words <$> getContents
  pretty 0 [] dat (args!!0)

試しにゲティスバーグ演説を66字幅で整形してみた。

Four score and seven years ago our fathers brought forth on this  
continent, a new nation, conceived in Liberty, and dedicated to   
the proposition that all men are created equal. Now we are engaged
in a great civil war, testing whether that nation, or any nation  
so conceived and so dedicated, can long endure. We are met on a   
great battle-field of that war. We have come to dedicate a portion
of that field, as a final resting place for those who here gave   
their lives that that nation might live. It is altogether fitting 
and proper that we should do this. But, in a larger sense, we can 
not dedicate - we can not consecrate - we can not hallow - this   
ground. The brave men, living and dead, who struggled here, have  
consecrated it, far above our poor power to add or detract. The   
world will little note, nor long remember what we say here, but it
can never forget what they did here. It is for us the living,     
rather, to be dedicated here to the unfinished work which they who
fought here have thus far so nobly advanced. It is rather for us  
to be here dedicated to the great task remaining before us - that 
from these honored dead we take increased devotion to that cause  
for which they gave the last full measure of devotion - that we   
here highly resolve that these dead shall not have died in vain - 
that this nation, under God, shall have a new birth of freedom -  
and that government of the people, by the people, for the people, 
shall not perish from the earth.                               

まあ、それなり。