[nat]
match true:bool with
[ true \Rightarrow O
| false \Rightarrow (S O)
]

[nat]
match O:nat with
[ O \Rightarrow O
| (S x) \Rightarrow (S (S x))
]

[nat]
match nil:list with
[ nil \Rightarrow nil
| (cons x y) \Rightarrow (cons x y)
]