I haven't really been following the discussion about the new camlp4, but it seems quite a lot has changed. I only use some fairly simple extensions to parsing (a few new infix names, and forcing anonymous expressions "..." to become "let it = ..."). However I also make two invasive changes to the lexer: * Modify the lexical rules for deciding whether a name is a regular or special identifier (not just based on case of the first letter) * Change the quotation delimiters to be `...` rather than <<...>> In the current camlp4, the only way I found to do this was basically to copy the existing lexer and edit it. Although it works, it's ugly and invariably means that I've had to change something with almost every new version of camlp4. Does the new camlp4 offer a nicer way of changing the lexer? John.