Hi Michael, Seeing as you thought my puzzle would be useful to the community, I thought that by the same logic you might want to update that sample you posted with the next thing I had to bust my brain over. parseRequestBody gave me a bit of a headache cos the only sample I could find was out of date and used something called lbsSink. I'm sure you'd want to tidy it up first... I'm also a bit worried about those (toHtml.show)s near the bottom. {-# LANGUAGE OverloadedStrings #-} module Main where import Network.Wai import Network.HTTP.Types import Network.HTTP.Types.Header (hContentType, hContentLength, hConnection) import Network.Wai.Handler.Warp (run) import Blaze.ByteString.Builder (fromByteString, fromLazyByteString) import qualified Data.ByteString.Char8 as BS import Data.Text import qualified Text.Blaze.Html5 as H (form) --import qualified Text.Blaze.Html5.Attributes as A import Text.Blaze.Html5 import Text.Blaze.Html5.Attributes import Text.Blaze.Html.Renderer.Utf8 import qualified Data.ByteString.Lazy as LB import System.Environment (getEnv) import Network.Wai.Parse (parseRequestBody, lbsBackEnd) application:: Application application req = parseRequestBody lbsBackEnd req >>= \(b,_) -> let (code, html) = app ((requestMethod req),(pathInfo req),(queryString req),b) in return $ ResponseBuilder code [ (hContentType, "text/html"), (hConnection, "keep-alive")] $ renderHtmlBuilder html app x = case x of ("GET", url, [], _) -> (status200, aform url) ("GET", url, qs, _) -> (status200, gform qs) ("POST", url, _, hsm) -> (status200, pform hsm) aform :: [Text] -> Html aform url = docTypeHtml $ do body $ do h3 "GETting form" H.form ! name "fooform" ! method "get" ! action "/in" $ ( mapM_ (\n -> (toHtml n) >> input ! name (toValue n) ! type_ "text" >> br ) url ) >> input ! type_ "submit" ! value "Submit" h3 "POSTting form" H.form ! name "fooform" ! method "post" ! action "/in" $ ( mapM_ (\n -> (toHtml n) >> input ! name (toValue n) ! type_ "text" >> br ) url ) >> input ! type_ "submit" ! value "Submit" gform :: [QueryItem] -> Html gform qs = docTypeHtml $ body $ do h3 "GETted form" mapM_ (\(n,mv) -> "The " >> ((toHtml.show) n) >> " is " >> maybe "" (toHtml.show) mv >> br) qs pform :: [(BS.ByteString, BS.ByteString)] -> Html pform hs = docTypeHtml $ body $ do h3 "POSTed form" mapM_ (\(n,v) -> "The " >> ((toHtml.show) n) >> " is " >> (toHtml.show) v >> br) hs main:: IO () main = getEnv "PORT" >>= flip run application . read Adrian. On 9 July 2013 21:16, Adrian May wrote:

Thanks! That's fantastic. Now I try to master that <*> trick to get something out of a post and then see if HaskellDB wants to eat it.

Adrian.

On 9 July 2013 18:03, Michael Snoyman wrote:

...

I've put together a more efficient version on School of Haskell:

https://www.fpcomplete.com/user/snoyberg/random-code-snippets/wai-blaze-html

The differences from yours are:

- Instead of turning your H.Html into a lazy ByteString and then into a Builder, this code goes directly to a Builder via renderHtmlBuilder. - No content-length header is included in the output, since that would require rendering the builder to a lazy bytestring, which would be an unnecessary buffer copy. - Doesn't use BS.pack, since OverloadedStrings makes it unnecessary.

On Tue, Jul 9, 2013 at 11:44 AM, Adrian May < adrian.alexander.may@gmail.com> wrote:

...

Hi All,

I just cobbled together the code below from a couple of samples, but got the types matched up by trial and error. I don't really understand when things are getting converted between lazy, strict, utf8, ascii, etc. I don't want ascii in the served page at all. Is it optimal?

TIA, Adrian

{-# LANGUAGE OverloadedStrings #-}

module Main where

import Network.Wai (Application, Response (ResponseBuilder)) import Network.HTTP.Types (status200) import Network.HTTP.Types.Header (hContentType, hContentLength, hConnection) import Network.Wai.Handler.Warp (run) import Blaze.ByteString.Builder (fromByteString, fromLazyByteString) import qualified Data.ByteString.Char8 as BS (pack, length)

import qualified Text.Blaze.Html5 as H import qualified Text.Blaze.Html5.Attributes as A import Text.Blaze.Html.Renderer.Utf8

import qualified Data.ByteString.Lazy as LB

application:: Application application _ = return $ ResponseBuilder status200 [(hContentType, BS.pack "text/html"), (hContentLength, BS.pack bodyLen), (hConnection, BS.pack "keep-alive")] $ fromLazyByteString body where body = root bodyLen = show. LB.length $ body

root = renderHtml rooth

rooth :: H.Html rooth = H.docTypeHtml $ do H.body $ do H.h1 "Hello"

main:: IO () main = run 8080 application

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