I've been doing some work on Hoogle 4 over the last week while I've been away from a computer. Lots of cool new ideas, some paper code, and other goodies - will probably be a few weeks before I start to crank out implementations and improvements get seen on the main Hoogle site, and perhaps 2 or 3 months before Hoogle 4 starts to take shape.
Anyway, one thing Hoogle needs to do is to output a web page, and at the moment it does that by reading in text files, and writing them out. To do a typical search page it shoves out a standard prefix, a top bit, the answers and a suffix. Only the answers are generated on the fly, the others are included in. Of course, this means that the HTML is in 4 places, and the reusability is poor (files are chunks of text, not functions). The pages also have small tweaks to them based on dynamic data - for example the title of the page is the search query. To accomodate this I had to add $ replacement, so $ becomes the search query. Messy, and not very general.
So to answer all this, I devised .ths - Textual Haskell Source. Currently you have .hs (source code is the main thing), .lhs (comments are the main thing) and now you have .ths (text is the main thing). Lets start with an example:
> showHtml :: String -> String
> showHtml search = pure
[title]<% search %> - Hoogle[/title]
Note that in this example I am escaping the code (with > ticks), and the text is just the main bit. I also have <% code %> which is substituted inline.
I can also do more advanced things (naturally)
> showList :: FilePath -> [Bool] -> IO String
> showList filename items =
> src <- readFile filename
The length of <% filename %> is <% length src %>
And the booleans are
<%for i = items %> <%if i %>ON<%else%>off<%end if%><%end for%>
I have all these bits implemented, and hope to make a release in a few days. I kind of have to release, because the current darcs version of Hoogle will be using them in a few days anyway.
And of course, since all this stuff is Haskell, its easier to compose, call as functions, etc.
Thoughts or comments?