so, to respond to my own post, what I need is a pair of brackets denoting a bag (aka multiset), rather than using curly braces which denote a set.
In other words, rather than
X = { a, b, c, … } .
I would like something like
X = / a, b, c, … \ .
with a proper pair of brackets, and the following sequences would be legal:
baaabaabcccaa
abc
bca
cab
cba
acb
bac
but these would not, albeit they are legal between {}:
a
ab
ac
null
bc
c
b
cccccccbbbbbbb
etc
From: BlackBox [mailto:BLACKBOX{([at]})nowhere.xy
Sent: 17 February 2012 11:23
To: BLACKBOX{([at]})nowhere.xy
Subject: Re: [BLACKBOX] EBNF question
I would put some of your restrictions in the syntax and some in the semantics.
Thanks Aubrey. It seems as though I have no choice in the matter! I'm just surprised that EBNF (and other notations) can't do what I want. I really don’t think is a semantic matter, it certainly feels more like a syntactic issue to me.
B
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Received on Fri Feb 17 2012 - 12:40:17 UTC