returns a (usually string) name of the RLink data type to which expr belongs.
- If expr is a valid RLink high-level representation of an R object, its type name (usually string) is returned. Otherwise, returns None.
- If expr matches the pattern of one of the currently registered extended RLink data types, RTypeOfHighLevelExpression[expr] returns the name of that type. If there is no such match but expr is a valid low-level RLink representation of an R object, "core" is returned.
- If there is more than one currently registered data type whose pattern matches expr, the name of the type first registered is returned. (Normally, the user who extends the type system should ensure that such type collisions do not occur. The recommended way to guarantee the absence of such collisions is to base the type dispatch/recognition on the "class" attribute of R objects.)