A <i>number</i> is a string of numeric characters ( <font face="Courier New">0123456789</font> ) with optional sign and decimal point ( <font face="Courier New">+ - .</font> ). The minus sign binds more tightly as a "negation" symbol than any mathematical operator. For instance, <font face="Courier New">-3^2</font> is interpreted as <font face="Courier New">(-3)*(-3) = 9</font>. To get <font face="Courier New">-9</font>, use <font face="Courier New">-(3^2)</font> or <font face="Courier New">-(-3^2)</font>.