markup-command and markup-command-list signatures

[David Kastrup]

Hi,

I am currently reworking the markup command parsing.  We have something
like

The available combinations of arguments (after the standard @var{layout}
and @var{props} arguments) to a markup command defined with
@code{define-markup-command} are limited as follows.

@table @asis
@item (no argument)
@itemx @var{markup-list}
@itemx @var{markup}
@itemx @var{markup markup}
@itemx @var{scheme}
@itemx @var{scheme markup}
@itemx @var{scheme scheme}
@itemx @var{scheme scheme markup}
@itemx @var{scheme scheme markup markup}
@itemx @var{scheme markup markup}
@itemx @var{scheme scheme scheme}
@end table

in the docs for markup command definitions, and nothing at all in the
docs for markup command list definitions as far as I can see.

What type signatures would be actually permissable under the assumption
that they are supported by lexer and parser?

It is somewhat clear to me that we can't have markup-list followed by
markup in the arguments.  Anything else?

-- 
David Kastrup