BlazeHtml 0.2

Second release of my GSoC project
Published on August 9, 2010 under the tag haskell

This is another blogpost about BlazeHtml – the project I am working on for Google Summer of Code for We are ready for a 0.2 release, which should fix all the issues with the 0.1 release.

Internal rewrite

Internally, most of it has been rewritten. The big advantage of our new internal system is that we can now support different backends, without losing any speed. We support the following backends for now:

Supported HTML versions

We’ve expanded the set of supported HTML versions as well. Blaze now supports:


Additionally, I’ve been working on a tool blaze-from-html (which needs to be separately installed using cabal install blaze-from-html) to convert HTML to blaze code.

[jasper@alice ~]$ curl -S | blaze-from-html -e | head
docTypeHtml ! xmlns "" ! lang "en" $ do
    H.head $ do
        H.title "Haskell - HaskellWiki"
        meta ! name "KEYWORDS" ! content "Haskell"
        meta ! http_equiv "Content-type" ! content "text/html; charset=utf-8"
        meta ! name "robots" ! content "index,follow"
        link ! rel "shortcut icon" ! href "/favicon.ico"
        link ! rel "copyright" ! href "/haskellwiki/HaskellWiki:Copyrights"

The -e flags ignores some errors, basically because the haskell homepage is XHTML, and blaze-from-html wants to read HTML.

As you can see, the produced code is prettified and indented. If you use the -s (standalone) flag, you will also get all the necessary imports and definitions, so you can directly compile the produced file.

Html type

Another big change is that we’ve changed the type for templates. From now on, all your templates will be of the type Html instead of Html (). We felt this choice is more sensible – we’re very sorry if this temporarily breaks your application.


As always, feedback is more than welcome! This is a community project, after all. If you’re interested, also check out the blogs of the other Google Summer of Code participants for!