John Goerzen
Possible, but ugly. I have about 50 lines of code that has to go in-between, so I'd be duplicating it. And, if I tried to make it into just another function, I'd have the same problem, I believe (scoping)
It's all much easier: as always, you just have to use template functions for all your pages. That's all you need ... :-) Here is a recipe how I typically structure my WASH applications: - First, I write down (html) code for all the web pages and abstract over all the varying parts (input fields, submit buttons, continuation pages, etc.). As result, I get (independent) template function for all the pages. Usually, each template function lives in a separate module/file. - In the end, I write a *controller* function that both generates all the different pages by filling the holes of the templates and also ties together all the consecutive pages. And that's all you need to solve your problem as well -- just use a template function twice! Below, you'll find a small web app that toggles between two varying input pages using the scheme I described above. -Matthias module Main where import CGI main = run controller -- controller controller :: CGI () controller = let input1 = tr $ td $ textInputField empty submit1 = \ h cont -> submit h cont empty page1 = stepOneTemplate input1 submit1 page2 out2 = \ t -> text t submit2 = \ cont -> submit0 cont empty page2 = stepTwoTemplate value out2 submit2 page3 input3 = empty submit3 = \ h cont -> submit F0 cont empty page3 = stepOneTemplate input3 submit3 page4 out4 = \ t -> text "No input, sorry!" submit4 = \ cont -> submit0 cont empty page4 = stepTwoTemplate (const undefined) out4 submit4 page1 in page1 -- page templates stepOneTemplate inputCode submitCode nextPage = do standardQuery "Input Page" $ table $ do do tr $ td $ text "Hello!" h <- inputCode tr $ td $ text "Press the button!" tr $ td $ submitCode h nextPage stepTwoTemplate validationCode outputCode submitCode nextPage h = do let i = validationCode h standardQuery "Result Page" $ table $ do tr $ td $ text "Your input was ..." tr $ td $ outputCode i tr $ td $ submitCode nextPage -- Matthias Neubauer | Universität Freiburg, Institut für Informatik | tel +49 761 203 8060 Georges-Köhler-Allee 79, 79110 Freiburg i. Br., Germany | fax +49 761 203 8052