While in emacs I called up the m4 info file, and read up to section "1.4 Using this manual".
There I saw: <begin snip> As each of the predefined macros in 'm4' is described, a prototype call of the macro will be shown, giving descriptive names to the arguments, e.g., -- Composite: example (STRING, [COUNT = '1'] [ARGUMENT]This is a sample prototype. There is not really a macro named 'example', but this documents that if there were, it would be <end snip> What is "[ARGUMENT]"? I assumed it was the start of that text. But the explanation later says: <begin snip> intended to call the macro without any arguments. The brackets around COUNT and ARGUMENT show that these arguments are optional. <end snip> So perhaps "[ARGUMENT]" is intended to be a dummy parameter in the example. Perhaps this section is formatted incorrectly. Emacs is: GNU Emacs 24.3.1 (i686-pc-linux-gnu, GTK+ Version 3.10.7) of 2014-03-07 on toyol, modified by Debian m4 manual is: manual (22 September 2013) for GNU M4 (version 1.4.17) This Lenovo N500 laptop is running Linux Mint 17.1 . Thanks very much.