Thank you all for the responses. Qualified imports for a script of less then a page make the code less readable. That is why I want to specifically import subsets of functions and not prefix everything with qualified imports. I've taken the code from Travis (clean up some of the useless pack/unpack), decided to use "NoImplicitPrelude" and then I had this: #!/usr/bin/runghc {-# LANGUAGE NoImplicitPrelude, OverloadedStrings #-} import Prelude (Show, IO, (++), print, String, filter) import Data.List (isSuffixOf) import Data.Text hiding (isSuffixOf, filter) import Data.Text.IO import Control.Monad (mapM_) import qualified Data.ByteString.Lazy as BL import System.Directory (getDirectoryContents) import System.FilePath.Posix ((<.>), FilePath, takeBaseName) import Data.Aeson data Product = Product { image :: Text , description :: Text } deriving Show instance ToJSON Product where toJSON (Product image description) = object ["image" .= image, "description" .= description] encodeToJson :: FilePath -> IO() encodeToJson srcName = do let jsonName = takeBaseName srcName <.> "json" contents <- readFile srcName let contentLines = lines contents case contentLines of -- head is unsafe! try your code on an empty file (firstLine : restLines) -> BL.writeFile jsonName (encode Product { image = firstLine, description = unlines restLines }) _ -> print ("error: invalid source file: " ++ srcName) main = do names <- getDirectoryContents "." let srcNames = filter (isSuffixOf ".src") names mapM_ encodeToJson srcNames What bugs me is that this is a really simple thing to do in any other language, but here I seem to be stuck between Prelude and Text and as a beginner Prelude is king. I tried ClassyPrelude but got stuck at not being able to get the result of getDirectoryContents into the ClassyPrelude version of mapM_. Sorry but I gave up on that. I think that given all this, the above code is as beautiful as Haskell can pull this off at the moment. If somebody can prove me wrong, I would love to still see it. Greetings, Bram On Sun, Mar 1, 2015 at 1:42 AM, Travis Cardwell wrote:

On 2015年02月28日 20:23, Bram Neijt wrote:

...

It quickly became a collection of "import qualified" and "T.unpack, T.pack" calls that made the whole thing look ugly [1]. <SNIP> [1] Source can be read here: https://gist.github.com/bneijt/9bdb4b1759790a8463c9

File paths are of type `System.FilePath.Posix.FilePath`, a type alias for `String`. Note that this convention is also followed in `ByteString` and `Text` libraries; they do not use `ByteString` or `Text` types for the file paths.

In this code, file paths are packed only to have to unpack them again (twice!), which likely offsets any performance improvements of using the `Text` version of `isSuffixOf`.

Here is a version using the same style but without packing file paths: https://gist.github.com/TravisCardwell/fd9981e4968e4af3751d

I included a few other changes, which are commented in the code.

By the way, I do not think that qualified imports are bad. I like them because they provide an explicit reference to the source module of a function.

Cheers,

Travis _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe

Thank you! I think that looks much better then anything I got working. Using another Prelude looks the best in this case, but without your help I would have never found system-fileio. Bram On Sun, Mar 1, 2015 at 5:52 PM, Michael Snoyman wrote:

The trick with ClassyPrelude is to use the system-fileio package instead of straight directory. With that in place, you get:

{-# LANGUAGE NoImplicitPrelude, OverloadedStrings #-} import ClassyPrelude import Data.Aeson import Filesystem (listDirectory)

data Product = Product { image :: Text , description :: Text } deriving Show

instance ToJSON Product where toJSON (Product image description) = object ["image" .= image, "description" .= description]

encodeToJson :: FilePath -> IO() encodeToJson srcName = do let jsonName = basename srcName <.> "json" contents <- readFile srcName let contentLines = lines contents case contentLines of -- head is unsafe! try your code on an empty file (firstLine : restLines) -> writeFile jsonName (encode Product { image = firstLine, description = unlines restLines }) _ -> print ("error: invalid source file: " ++ srcName)

main = do names <- listDirectory "." let srcNames = filter (flip hasExtension "src") names mapM_ encodeToJson srcNames

On Sun, Mar 1, 2015 at 6:47 PM Bram Neijt wrote:

...

Thank you all for the responses.

Qualified imports for a script of less then a page make the code less readable. That is why I want to specifically import subsets of functions and not prefix everything with qualified imports.

I've taken the code from Travis (clean up some of the useless pack/unpack), decided to use "NoImplicitPrelude" and then I had this:

#!/usr/bin/runghc {-# LANGUAGE NoImplicitPrelude, OverloadedStrings #-} import Prelude (Show, IO, (++), print, String, filter) import Data.List (isSuffixOf) import Data.Text hiding (isSuffixOf, filter) import Data.Text.IO import Control.Monad (mapM_)

import qualified Data.ByteString.Lazy as BL import System.Directory (getDirectoryContents) import System.FilePath.Posix ((<.>), FilePath, takeBaseName)

import Data.Aeson

data Product = Product { image :: Text , description :: Text } deriving Show

instance ToJSON Product where toJSON (Product image description) = object ["image" .= image, "description" .= description]

encodeToJson :: FilePath -> IO() encodeToJson srcName = do let jsonName = takeBaseName srcName <.> "json" contents <- readFile srcName let contentLines = lines contents case contentLines of -- head is unsafe! try your code on an empty file (firstLine : restLines) -> BL.writeFile jsonName (encode Product { image = firstLine, description = unlines restLines }) _ -> print ("error: invalid source file: " ++ srcName)

main = do names <- getDirectoryContents "." let srcNames = filter (isSuffixOf ".src") names mapM_ encodeToJson srcNames

What bugs me is that this is a really simple thing to do in any other language, but here I seem to be stuck between Prelude and Text and as a beginner Prelude is king.

I tried ClassyPrelude but got stuck at not being able to get the result of getDirectoryContents into the ClassyPrelude version of mapM_. Sorry but I gave up on that.

I think that given all this, the above code is as beautiful as Haskell can pull this off at the moment.

If somebody can prove me wrong, I would love to still see it.

Greetings,

Bram

On Sun, Mar 1, 2015 at 1:42 AM, Travis Cardwell wrote:

...

On 2015年02月28日 20:23, Bram Neijt wrote:

...

It quickly became a collection of "import qualified" and "T.unpack, T.pack" calls that made the whole thing look ugly [1]. <SNIP> [1] Source can be read here: https://gist.github.com/bneijt/9bdb4b1759790a8463c9

File paths are of type `System.FilePath.Posix.FilePath`, a type alias for `String`. Note that this convention is also followed in `ByteString` and `Text` libraries; they do not use `ByteString` or `Text` types for the file paths.

In this code, file paths are packed only to have to unpack them again (twice!), which likely offsets any performance improvements of using the `Text` version of `isSuffixOf`.

Here is a version using the same style but without packing file paths: https://gist.github.com/TravisCardwell/fd9981e4968e4af3751d

I included a few other changes, which are commented in the code.

By the way, I do not think that qualified imports are bad. I like them because they provide an explicit reference to the source module of a function.

Cheers,

Travis _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/haskell-cafe

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