> How do you model/maintain invariants of a set of data in FP? That's the part that I don't understand yet. If you tell me how you do it in not-FP then I'll te

> How do you model/maintain invariants of a set of data in FP? That's the part that I don't understand yet. If you tell me how you do it in not-FP then I'll tell you how to do it in FP!