ever, even well-formed JSON is not guaranteed to decode.  Two common kinds of error situations result from implementation restrictions on character codes and on floating-point reals.  If the decoder encounters in a JSON string an escape sequence <code class="json-literal">\u<var>XXXX</var></code> where <var>XXXX</var> is the hexadecimal presentation of a number <var>N</var> which either exceeds the implementation's <code class="other-name">char-code-limit</code> or for which <code class="api-name">code-char