Idris2-boot/tests/idris2/coverage002/Vect.idr
Edwin Brady 04e4ebf80e Better approach to erasure in pattern matching
It's a big patch, but the summary is that it's okay to use a pattern in
an erased position if either:

- the pattern can also be solved by unification (this is the same as
  'dot patterns' for matching on non-constructor forms)
- the argument position is detaggable w.r.t. non-erased arguments, which
  means we can tell which pattern it is without pattern matching

The second case, in particular, means we can still pattern match on
proof terms which turn out to be irrelevant, especially Refl.

Fixes #178
2020-01-21 18:47:43 +00:00

46 lines
1.6 KiB
Idris

data Vect : Nat -> Type -> Type where
Nil : Vect Z a
(::) : a -> Vect k a -> Vect (S k) a
append : Vect n a -> Vect m a -> Vect (n + m) a
append [] ys = ys
append (x :: xs) ys = x :: append xs ys
-- Primarily to check the number of cases in the totality checker doesn't
-- explode because of all the Nils and Nats
funny : Vect 4 Bool -> Int
funny [False, False, False, False] = 0
funny [False, False, False, True] = 1
funny [False, False, True, False] = 2
funny [False, False, True, True] = 3
funny [False, True, False, False] = 4
funny [False, True, False, True] = 5
funny [False, True, True, False] = 6
funny [False, True, True, True] = 7
funny [True, False, False, False] = 8
funny [True, False, False, True] = 0
funny [True, False, True, False] = 10
funny [True, False, True, True] = 11
funny [True, True, False, False] = 12
funny [True, True, False, True] = 13
funny [True, True, True, False] = 14
funny [True, True, True, True] = 15
notFunny : Vect 4 Bool -> Int
notFunny [False, False, False, False] = 0
notFunny [False, False, False, True] = 1
notFunny [False, False, True, False] = 2
-- notFunny [False, False, True, True] = 3
notFunny [False, True, False, False] = 4
notFunny [False, True, False, True] = 5
notFunny [False, True, True, False] = 6
-- notFunny [False, True, True, True] = 7
notFunny [True, False, False, False] = 8
notFunny [True, False, False, True] = 0
notFunny [True, False, True, False] = 10
notFunny [True, False, True, True] = 11
notFunny [True, True, False, False] = 12
notFunny [True, True, False, True] = 13
notFunny [True, True, True, False] = 14
notFunny [True, True, True, True] = 15