* Multithreading (current version is probably thread-safe but any threading 
  code is missing)
* More number types:
  - Big integers
  - Fractions
  - Complex numbers (as pairs of two numbers of same type)
* caaadadr and such weird functions (I've no idea how to implement this)
* IO
* Garbage collected symbols
* Documentation for library API
* Documented semantics of locales
* Unicode case-insensitive string compare
* Some platform- and locale-independent conversion of numbers from/to strings
* iteration (do and posible common-lisp style loop)