Cool, I love having stuff like this out there. It may not always be the right tool for a given problem, but sometimes it will be. I imagine I'll have cause to use it sometime this year, so thanks!
In particular, I could see this being useful in a situation where you want the validation "rule" to be readable by non-programmers (perhaps if building a system where an end-user can choose amongst a set of canned validation rules for custom fields that they can add to something-or-other). In such a case, this simple grammar is something you could display in whatever "configurator" UI the user has. In general I like stuff that both programmers and non-programmers (or just a programmer that doesn't feel like being a programmer right then) can understand.
In particular, I could see this being useful in a situation where you want the validation "rule" to be readable by non-programmers (perhaps if building a system where an end-user can choose amongst a set of canned validation rules for custom fields that they can add to something-or-other). In such a case, this simple grammar is something you could display in whatever "configurator" UI the user has. In general I like stuff that both programmers and non-programmers (or just a programmer that doesn't feel like being a programmer right then) can understand.
Thanks for taking the time to post it laktek.