} else if(tag.equals(MathExpressionConstValueDouble.TAG)) {
express = new MathExpressionConstValueDouble(element,
cf.getChildContext(MathExpressionConstValueDouble.GROUP));
} else if(tag.equals(MathExpressionConstValueDate.TAG)) {
express = new MathExpressionConstValueDate(element,
cf.getChildContext(MathExpressionConstValueDate.GROUP));
} else if(tag.equals(MathExpressionConstValueString.TAG)) {
express = new MathExpressionConstValueString(element,
cf.getChildContext(MathExpressionConstValueString.GROUP));