} else if(tag.equals(MathExpressionConstValueNull.TAG)) {
express = new MathExpressionConstValueNull(element,
cf.getChildContext(MathExpressionConstValueNull.GROUP));
} else if(tag.equals(MathExpressionConstValueBoolean.TAG)) {
express = new MathExpressionConstValueBoolean(element,
cf.getChildContext(MathExpressionConstValueBoolean.GROUP));
} else if(tag.equals(MathExpressionConstValueLong.TAG)) {
express = new MathExpressionConstValueLong(element,
cf.getChildContext(MathExpressionConstValueLong.GROUP));