Anton Tayanovskyy wrote:
As a weekend hack, I just realized that Haskell has this wonderful DoRec syntax that among other things seems to be able to let the user express context-free grammars together with their processing rules in normal Haskell code, without template Haskell or anything like that, just like parser combinators.
I am just wondering if this is this a known and useful result? Are there libraries doing similar stuff?
John Meacham's frisby library [1] did something similar, though the technique is not as well-known as it should be. Note that you don't need to give explicit names to your rules anymore, the monad can do that for you. By the way, the old mdo notation was better suited to this task; the new rec notation has some problems in this regard that will hopefully be rectified soon. [1]: http://repetae.net/computer/frisby/#v%3AnewRule Best regards, Heinrich Apfelmus -- http://apfelmus.nfshost.com