"Joel E. Denny" <[EMAIL PROTECTED]> writes: > I suspect that using [] in a grammar to mean optional is not nearly as > common.
It's pretty common, I'm afraid. It's in the ISO standard for EBNF, for example. http://www.cl.cam.ac.uk/~mgk25/iso-ebnf.html Characters unused by ISO EBNF include .:!+_%@&#$<>/\^`~. I sort of liked the notation a.b to denote the b component of a, as it's a common notation in many languages. But I admit I haven't been following this discussion too closely.
