Arbitrary precision integers are supported if GMP is installed. A new datatype called mapping . It behaves almost lika vectors, except that you may reference it using other types than integers. Mappings are in many cases almost as fast as vectors. Identifiers are case sensitive.
Strings are always immutable, e.i.
The compiler is, almost, two-pass. Strings and symbols are shared. Eval compiles its expression before evaluating it. Mappings are self-resizable, i.e. you don't have to worry about them being too small or too big. The number notation of R 5 RS is supported and exceeded.