-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 On Sat, Dec 20, 2008 at 4:55 AM, Neil Mitchell wrote:

Hi,

I am pleased to announce HLint, a tool for making suggestions to improve your Haskell code. Previously this tool was called Dr Haskell and depended on a working installation of Yhc - both of those have now changed. HLint requires GHC 6.10*, and to install simply type:

cabal update && cabal install hlint

If you haven't yet installed the cabal command, instructions are here: http://ghcmutterings.wordpress.com/2008/11/10/bootstrapping-cabal-install/

As an example of what HLint does, running "hlint darcs-2.1.2" over the latest stable release of darcs gives 385 suggestions, including:

darcs-2.1.2\src\CommandLine.lhs:46:1: Use a string literal Found: [' ', '\t', '"', '%'] Why not: " \t\"%"

darcs-2.1.2\src\CommandLine.lhs:49:1: Eta reduce Found: quotedArg ftable = between (char '"') (char '"') $ quoteContent ftable Why not: quotedArg = between (char '"') (char '"') . quoteContent

darcs-2.1.2\src\CommandLine.lhs:94:1: Use concatMap Found: concat $ map escapeC s Why not: concatMap escapeC s

To see all the hints in a nice interactive document visit http://www-users.cs.york.ac.uk/~ndm/hlint/hlint-report.htm (recommended if you are thinking of trying out hlint)

All necessary links, including a manual, hackage links, bug tracker and source code can be found from the tool website: http://www-users.cs.york.ac.uk/~ndm/hlint/

Acknowledgements: Niklas Broberg and the haskell-src-exts package have both been very helpful. The darcs users mailing list gave many good suggestions which I've incorportated.

Please direct any follow up conversations to haskell-cafe@

Thanks

Neil

* Why GHC 6.10? View patterns.

Hi, Neil. Thanks for the tool; it found some worthwhile changes in my projects. But a few points: 1) How does one actually use the CLI tool? You didn't say. It *seems* that one just feeds it a list of random filepaths, so on Mueval, say, the command would be 'hlint main.hs Mueval/*.hs' (and not, say, 'hlint mueval.cabal'). But I'm not actually sure. 2) I think I found a parsing bug. One line in Mueval/Interpreter.hs runs:

fmap (take n exceptionMsg ++) $ render' (n-length exceptionMsg) s

which gives the error:

Mueval/Interpreter.hs:145:59: Parse failure, Parse error No relevant suggestions

Adding spaces between 'n' and 'length', so it reads:

fmap (take n exceptionMsg ++) $ render' (n - length exceptionMsg) s

lets hlint parse and suggest for it. - -- gwern -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEAREKAAYFAklM+kwACgkQvpDo5Pfl1oKDhwCfRgQutbvr9QbKvbLJlbhdla2Z absAniWC+ksXHhfbunsdOsnmG69lppFZ =X9uv -----END PGP SIGNATURE-----