Hello all, One question occurs to me about xparse "processors". I've provided one that splits on a comma, \xparse_process_comma_split:n. I wonder what the behaviour of this type of function should be if the input is not of the correct form. At the moment, if you apply a processor to an optional argument and no value is given, the special \NoValue token is left alone. The normal behaviour for this function is: \xparse_process_comma_split:n { 1,2 } => {1} {2} but what should happen with \xparse_process_comma_split:n { 12 } A the moment you get "{12} \NoValue" so that exactly two results are returned. Should you get perhaps just \NoValue, or something else? -- Joseph Wright