Re: [Haskell-cafe] Web application interface

Excerpts from Michael Snoyman's message of Thu Jan 14 17:32:26 +0100 2010:

On Thu, Jan 14, 2010 at 5:42 PM, Jeremy Shaw wrote:

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I wonder if the 'Response' portion of WAI should support all three currently used methods: - lazy I/O - Enumerator - sendFile

[...] As for your proposal of three methods, I'm not sure if it's necesary. I understand that we would want sendfile for speedy serving of files straight from the filesystem, but it's fairly straight-forward to convert a lazy bytestring into an enumerator, and I don't think we get a performance penalty for doing so (if there's a benchmark otherwise, I'd be happy to see it).

It is indeed easy to convert a lazy bytestring to an enumerator. What is not easy IMHO is to manipulate enumerators. I don't know if it is an issue in the context of using Wai/Hack, but for instance writing hack middleware could become a lot less fun. To be very specific how would you adapt hack-middleware-gzip [1] ? Regarding the unsafeness of lazy IO. I would like to recall the existence of safe-lazy-io [2] which was announced and explained here [3]. Best regards, [1]: http://hackage.haskell.org/package/hack-middleware-gzip [2]: http://hackage.haskell.org/package/safe-lazy-io [3]: http://www.haskell.org/pipermail/haskell/2009-March/021133.html -- Nicolas Pouillard http://nicolaspouillard.fr