Has anyone given thought to recursive structural regular expressions? I didn't see a way to do recursion from reading the paper and experimenting.
The reason for recursion would be that instead of having hopped-up regexes, we'd now have context-free expressions. Yacc needing tokens makes doing CF things a pain, but I think if grep, sed, sam, etc understood a simple CF expression language, we'd have something that was (mathematically) more powerful. One (perhaps silly) example is that you could see if your source code had balanced parens/braces/brackets/tags in a jiffy, but other examples include searching through records with complex structure. I suppose it would likely be too slow, but would it cost anything when it's not used?
