se:

<pre><tt>  SEMI, PLUS, MINUS, TIMES, DIVIDE, MOD, NUMBER, LPAREN,</tt>
and <tt>RPAREN</tt></pre>

The experienced user will note a problem with the above grammar.  It is
ambiguous.  An ambiguous grammar is a grammar which, given a certain
input, can reduce the parts of the input in two different ways such as
to give two different answers.  Take the above grammar, for
example. given the following input: <br>
<tt>3 + 4 * 6</tt><br>
The grammar can either evaluate the <tt>3 + 4</tt> and then multiply
seve