spec arg forms meaning ~~~~ ~~~~~~~~~ ~~~~~~~~ u \cmd unexpanded/unbraced token n \cmd {\cmd} token name c \cmd {\cmd1\cmd2...} container; the contents will be passed as argument [\expandafter{\cmd}] l \cmd {\cmd1\cmd2...} token list x \cmd {\cmd1\cmd2...} expanded token list A further spec is to be used with \exp_args: d \cmd {\cmd} dormant; usually n but it will not be expanded in protected expansions. ....... and uppercase variants of these. Interesting. I Would need to experiment a bit more with it before really commenting, but in anycase having some control over arguments in protected contexts must be useful (even in etex which has some primitive protection mechanism) > Actually, the problem is always present if diferent variants of > \exp_args and command specs are mixed: \exp_args:Noox\cmd:nNxn... > What? :-) ) Yes the current exp_arg schemes really assume that the underlying command is of type nnnn (or possibly some N's). If you apply it to something that already has a `different' argument type you get a mess. > So \def:Npn #1{\tex_def:D #1} instead > of \let:NN\def:Npn\tex_def:D. In the notation above that gives > \def:npl \def:npx \def:Npl \def:Npx. The whole question of what to do with the primitives is not clear. Initially the names like \def:Npn were defined in the initial pass through the TeX primitives. That is, each primitive was given a new name (and then the old name undefined). While descripibing the system for the paper at TUG98 this summer we decided to switch to a regular naming scheme for the primitives of \tex_(old name):D and then \let them to useable name(s) in the appropriate module (or modules). This does `waste' some csnames (as the :D forms are not supposed to be used) and it does let evil people like Phil reconstruct plain TeX by relocating all the primitive commands in a consistent way, but it seemed better than trying to decide the `right' new name for the primitives. The hope was that apart from these low level modules most code would be using (slightly) higher level functions in which the argument conventions were more rationalized. David