[started section on templating Jeremy Shaw **20100531231940 Ignore-this: 2e95a671bd39d0f46494ed6d2555a5ae ] hunk ./Makefile 5 -DEPS := HelloWorld.lhs RouteFilters.lhs +DEPS := HelloWorld.lhs RouteFilters.lhs Templates.lhs hunk ./Makefile 19 - runhaskell gen-toc.hs > toc.html + runhaskell gen-toc.hs $^ > toc.html addfile ./Templates.lhs hunk ./Templates.lhs 1 + + + + Crash Course in Happstack + + + + + +

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+

Templating and HTML

+ +

Happstack supports a number of third party templating and HTML +libraries. It is easy to add support for additional libraries, if your +favorite does not already have support.

+ +

Each templating system has it's own set of advantages and drawbacks.

+ +
+
HSP
+

HSP allows you to embed literal XML syntax inside your Haskell code. A pre-processor rewrites the literal XML into normal haskell function calls, and then the code is compiled.

+

pros:

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    +
  • Templates are compiled, so they are pretty fast (needs more benchmarks to support this statement however)
    • +
  • You have the full power of Haskell in your templates, because it is Haskell (with a purely syntactic extension)
    • +
  • Type-checked at compile time to ensure types are correct and no template values are missing
    • +
  • Syntax is very similar to XML/HTML, so it is easy to learn
    • +
  • Can be easier to work with when trying to populate a template from a complex Haskell type +
  • Can be used to generate HTML or XML
    • +
+

cons:

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  • Requires you to recompile in order to update the template
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  • Error messages are sometimes misleading or hard to understand
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  • Makes it easy to mix the application logic and view code together, making it hard to update later (therefore you must have self control)
    • +
  • Only suitable for generating XML and HTML documents
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  • Not ideal for having templates written by a non-programming web designer (although the xml syntax helps)
    • +
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+
BlazeHtml
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Hamlet
+
HStringTemplate
+
Heist
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more to come..
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+ + + + hunk ./gen-toc.hs 3 -import Data.List (groupBy) +import Control.Applicative +import Data.List (groupBy, isSuffixOf) hunk ./gen-toc.hs 9 +import System.Environment (getArgs) hunk ./gen-toc.hs 54 - do hs <- fmap concat $ mapM getHeaders files + do files <- filter (isSuffixOf ".html") <$> getArgs + hs <- fmap concat $ mapM getHeaders files