type S = SNil
       | SAtom { CString }
       | SCons { S[], S[] }
       | SPointer { ?[] }

.into : (S, Type<String>) -> String

== : (S, S) -> Bool

!= : (S, S) -> Bool

< : (S, S) -> Bool

<= : (S, S) -> Bool

> : (S, S) -> Bool

>= : (S, S) -> Bool