[help-texinfo] Determine if an argument was supplied to a macro

[Pantxo Diribarne]

Hello,

I'd like to define my own wrappers around @*ref macros so that they display
differently for plaintext outputs (don't want to see "Note..." in a static
text string).
My problem is to determine if a specific argument, among the 5 possible
ones, has been supplied or not.

If I assume the first arg is always supplied and only want to display this
one, this would be

@macro  myxref{arg1, arg2, arg3, arg4, arg5}
@ifplaintext
\arg1\
@end ifplaintext
@ifnotplaintext
xref{\arg1\, \arg2\, \arg3\, \arg4\, \arg5\}
@end ifnotplaintext
@end macro

Now how would I go if I want to display the third argument in case it's
supplied and the first in case arg3 is empty?

Thanks,

Pantxo