Hello, It might be handy to have a check to see if a value is any quark, for "make safe" code. So far, I've ended up with: \def_new:Npn \if_quark:NT #1 { \exp_after:NN \exp_after:NN \exp_after:NN \if_quark:w \exp_after:NN \token_to_string:N #1 \q_stop } \def_new:Npn \if_quark:wT #1#2#3\q_stop { \int_compare:nNnT {\char_value_uccode:n{#2}} = {`Q} } which seems to work but I'm worried may not be suitable more generally. Any ideas? -- Joseph Wright