public IVPNumber searchSubstring(IVPString sub, Context c, DataFactory factory) {
		IVPNumber result = factory.createIVPNumber();
		result.setValueType(IVPValue.INTEGER_TYPE);
		c.addInt(result.getUniqueID(), c.getString(getUniqueID()).indexOf(c.getString(sub.getUniqueID())));
		return result;
	}