Hi all, I am looking for a way to define an environment that takes a range as an optional argument. This should be given in the following way: \begin{environment}(15:5.23) with a default value, say (1:3). The two limits should then be parsed as single arguments which are separated by the colon. I am trying to do this with xparse and got some possible solutions with the u and d argument type, but I didn’t manage to get the parentheses optional. I guess what I need is some kind of an optional u argument … Does anyone have a suggestion how to easily implement these requests? cheers Arno