public void evaluate(List<Parameter> params) {
		if (fi == null)
			try {
				setFormula(formula);
			} catch (Exception e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		for (Parameter p : params) {
			if (fi.hasVariable(p.name)) {
				fi.setVariable(p.name, p.value);
			}
		}
		value = fi.evaluate();
	}