r arithmetic silently overflows. </li>

<li> Most arithmetic operators are omitted; only 1+, 1-, +, -,
     quotient, and remainder are present. </li>

<li> Very many standard library procedures are missing.  Only the
     following 55 procedures were actually present last time I updated
     this list: <tt>procedure? 
     string?
     make-string string-set! string-ref string-length car cdr cons
     pair? symbol? symbol-&gt;string string-&gt;symbol display newline eq?
     current-input-port read-char in