>> Do we care about keeping braces surrounding an element in a sequence >> (I'd say yes, although it requires more care)? > > Absolutely, yes. More on that. Many of the functions in the seq module are defined somewhat like \cs_new:Npn \seq_foo:w \seq_elt:w #1 \seq_elt_end: {... #1 ...} This removes braces around #1. Since the documentation explicitly states that seq can contain any token except `\seq_elt:w` and `\seq_elt_end:`, I started reimplementing many of the functions to avoid removing braces. However, I'm now seeing that "We use explicit delimiters instead of braces around text to allow efficient searching for an item in the sequence." But that won't work if the item contains `{`, `}`, or `#`. **So my question is: do we want to support braces in seq items or not?** One option would be to say yes, and provide two search functions: one quick one if the item does not contain braces nor `#`, and a slower one which recurses through the arguments and compares with `\tl_if_eq:nnTF`. -- Regards, Bruno