I stumbled on the following quirk recently: \tl_clear:N \l_tmpa_tl \fp_eval:n { round( \l_tmpa_tl, 4) } gives 4 as the answer (or whatever the rounding value is). Usually, in the situation where this arose, \l_tmpa_tl is a string of digits possibly including a decimal point. In this instance it was empty. Okay, I can check for that, but I wonder if l3fp should do so, and either give an error, as \fp_set:Nn \l_tmpa_fp { \l_tmpa_tl } does when the token list is empty, or give a conventional 0 as answer? Andrew --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus