Looks really interesting. I wrote an SQL parser and compiler frontend for a SQLite-style database last summer. I started off in C using Lex/Yacc, but for the last piece of the project I used Haskell. This step was to take SRA ("sugared relational algebra"), which is essentially a transition step between SQL and simple relational algebra, and desugar it into relational algebra. The code is up at <a href="https://github.com/thinkpad20/sql" rel="nofollow">https://github.com/thinkpad20/sql</a> if anyone is interested, with the code for that portion being contained in the haskell folder. I might translate the whole thing into Haskell (maybe using Attoparsec) at some point.<p>I was curious that you used a different version of relational algebra than the one I had been taught. I've usually seen RA described in terms of six fundamental operators: Project (pi), Select (sigma), Rename (rho), Cross Product, Union and Difference. What gave rise to the model you chose?<p>Anyway, it's great to see that more people are using Haskell. I would love to be able to work in it some day.
<i>I think it is worth taking the risk to use a relatively unusual and unproven technology.</i><p>should be:<p><i>I think it is worth taking the risk to use a relatively unusual technology.</i>