[Haskell-cafe] Infinite loop?

[Ralf Hinze]

Am Freitag 17 Februar 2006 21:12 schrieb rgo:
> Hi all,
> my program probably goes into infinite loop... But i cannot understand where and why.
> 
> code:
> 
> import System.Directory
> 
> data MyFile = MyDir {
>                 dir_name :: String,
>                 dir_files :: [MyFile]
>         }
>         | MyFile {
>                 file_name :: String
>         }
> 
> read_dir_entries :: [FilePath] -> IO [MyFile]
> read_dir_entries [] = return []
> read_dir_entries (name:names) = do
>         isdir <- doesDirectoryExist name;
>         entry <- if isdir
>                         then read_dir name
>                         else return (MyFile {file_name = name});
>         entries <- read_dir_entries names;
>         return (entry:entries)
>         
> 
> read_dir :: FilePath -> IO MyFile
> read_dir name = do 
>         content <- getDirectoryContents name;
>         files <- read_dir_entries content;
>         return MyDir {
>                 dir_name = name,
>                 dir_files = files
>         }
> 
> instance Show MyFile where
>         show (MyDir {dir_name = name, dir_files = files}) = 
>                 "\n" ++ name ++ ":\n" ++ show files
>         show (MyFile {file_name = name}) = "\t" ++ name ++ "\n"
> 
> main = do
>         cwd <- getCurrentDirectory;
>         dir <- read_dir cwd;
>         print dir;

Maybe because the file system is a graph not a tree (. and ..)?