Feature debate: range patterns

[protz]

It would be convenient to do:

match e₁ with pattern
-- Cons1 .. Cons2: e₂

where the pattern matches any constructors present in the enumeration declaration between Cons1 and Cons2.

This, of course, poses problems, such as semantics changing when constructors are re-ordered. But, in my use-case, I have something like:

declaration enumeration Violation:
  -- Section286_102   # Licensing
  -- Section291_2     # Reckless driving of vehicle or riding of animals; penalty
  -- Section291_3_1   # Consuming or possessing intoxicating liquor while operating motor vehicle or moped
  -- Section291_3_2   # Consuming or possessing intoxicating liquor while a passenger in a motor vehicle
  -- Section291_3_3   # Storage of opened container containing intoxicating liquor or consumption at scenic lookout
  -- Section291_4_6   # Driving after license suspended or denied for noncompliance with an order of support
  -- Section291_8     # Freight on motor cars; projection of, prohibited
  -- Section291_9     # Freight; on running board
  -- Section291_11_5  # Child passenger restraints
  -- Section291_11_6  # Mandatory use of seat belts, when, penalty
  -- Section291_11    # Riders and passengers under seven years of age on motorcycles and motor scooters prohibited
  -- Section291_12    # Inattention to driving
  -- Section291_13    # Traffic laws apply to persons driving mopeds
  -- Section291_14    # Pickup trucks; passenger restrictions

and oftentimes, say in a followup statute, there will be something like "for infractions between 291-X and 291-Y"... I don't want to switch to pairs of integers (because I would lose the benefits of exhaustiveness checking), so an alternative might be to enforce that such patterns impose that the type declaration constructors be sorted by lexicographic order

[denismerigoux]

Thanks Jonathan! I guess in the meantime you can hide that verbose matching in a helper variable, so that lawyers don't have to review this big pattern match. I'm not a fan of this lexicographic ordering enforcement, since in other situations you may want to group cases together in the type declaration in a way that is more semantic than lexicographic.