cf. HaHaHa! - ハイフンで区切られた文字をキャピタライズ
cf. 趣味的にっき - ハイフンで区切られた文字をキャピタライズ
↑ここら辺を見て思い出したのが，Ruby on Rails （より正確には ActiveSupport）にある String#underscore。
String#underscore は大文字/小文字/数字からなる文字列を小文字/数字/アンダースコアからなる文字列に変換するメソッドで……つまりこんな感じ。
D:\>irb -rrubygems -ractive_support --simple-prompt >> [ "Railes", ?> "ActiveSupport", ?> "Active1Support", ?> "Active1support", ?> "ToDoList", ?> "XML", ?> "XML2", ?> "XMLData", ?> "XMLdata", ?> "XML2Data", ?> "Iso2022jpMailer" >> ].each do |s| p s.underscore end "railes" "active_support" "active1_support" "active1support" "to_do_list" "xml" "xml2" "xml_data" "xm_ldata" "xml2_data" "iso2022jp_mailer" => ["Railes", "ActiveSupport", "Active1Support", "Active1support", "ToDoList", " XML", "XML2", "XMLData", "XMLdata", "XML2Data", "Iso2022jpMailer"]
これを Haskell でやってみた。
'_' は大文字の直前に入るんだけど，前後の文字によって入ったり入らなかったりで，ちょっと複雑。なので State モナドを使ってみた。
import Control.Monad.State import Data.Char import System.Environment data CharCase = UpperB4Upper | UpperB4Lower | UpperB4Number | UpperAtEnd | Lower | Number | None cState :: Char -> CharCase cState c | isUpper c = UpperB4Upper | isLower c = Lower | otherwise = Number procChar :: Char -> State CharCase [Char] procChar c = get >>= p where p UpperB4Upper = do put $ cState c return [toLower c] p UpperB4Lower = do put $ cState c return $ "_" ++ [toLower c] p UpperB4Number = do put $ cState c if isUpper c then return [toLower c] else return $ "_" ++ [c] p UpperAtEnd = do put $ cState c if isUpper c then return [toLower c] else return $ "_" ++ [c] p Lower | isUpper c = do put (UpperB4Lower) return [toLower c] | otherwise = do put $ cState c return [c] p Number | isUpper c = do put (UpperB4Number) return [toLower c] | otherwise = do put $ cState c return [c] p None = do put $ if isUpper c then UpperAtEnd else cState c return [toLower c] underScoreR :: String -> State CharCase String underScoreR s = do strs <- mapM procChar $ reverse s return $ reverse $ concat strs underScore :: String -> String underScore s = evalState (underScoreR s) None
UpperAtEnd は UpperB4Number と扱いが同じだから無くてもいいかも。
チェック用関数。
samples = [ ( "Rails" , "rails" ) , ( "ActiveSupport" , "active_support" ) , ( "Active1Support" , "active1_support" ) , ( "Active1support" , "active1support" ) , ( "ToDoList" , "to_do_list" ) , ( "XML" , "xml" ) , ( "XML2" , "xml2" ) , ( "XMLData" , "xml_data" ) , ( "XMLdata" , "xm_ldata" ) , ( "XML2Data" , "xml2_data" ) , ( "Iso2022jpMailer" , "iso2022jp_mailer" ) ] checkSamples = mapM_ (putStrLn . check) samples check s = (show $ underScore org == uds) ++ " " ++ org ++ " => " ++ uds where org = fst s uds = snd s
実際にやってみると
*Main> checkSamples Loading package mtl-1.0 ... linking ... done. True Rails => rails True ActiveSupport => active_support True Active1Support => active1_support True Active1support => active1support True ToDoList => to_do_list True XML => xml True XML2 => xml2 True XMLData => xml_data True XMLdata => xm_ldata True XML2Data => xml2_data True Iso2022jpMailer => iso2022jp_mailer
OKみたい。
