pr
               | ( boolexpr )
               | ! boolexpr
               | boolexpr & boolexpr
               | boolexpr | boolexpr
               ;
 </pre>

 Code example 1:
 <pre>
 String expr = "pow(BASE,EXPONENT)*MULT";
 HashMap symbols = new HashMap();
 symbols.put("BASE", new Double(2));
 symbols.put("EXPONENT", new Double(9));
 symbols.put("MULT", new Double(0.1));
 double result = MathematicalExpression.evaluate(expr, symbols);
 System.out.println(expr + " and " + symbols + " = " + result);
 </pr