lean2/tests/lean/unzip_error.lean

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import data.vector
open nat vector prod
variables {A B : Type}
definition unzip : Π {n : nat}, vector (A × B) n → vector A n × vector B n,
unzip nil := (nil, nil),
unzip ((a, b) :: v) :=
match unzip v with
(va, vb) := (a :: va, b :: vb)
end
example : unzip ((1, 20) :: (2, 30) :: nil) = (1 :: 2 :: nil, 20 :: 30 :: nil) :=
rfl