Re: parser generator terminology

Chris F Clark wrote:
>>> While I'm not so foolish as to argue with Waite, Goos, or the Bison
>>> maintainers, epseically when I've Seen V, VT, and VN used rather
>>> universally as the 3 sets of all symbols, terminals, and
>>> non-terminals, there is precedence for vocbulary as VT, given that
>>> Terence Parr uses it in ANTLR if I recall correctly.


>> This is not formally wrong: V can be any finite set of symbols. A
>> language is then a subset of V*. So it is OK to define a language L as a
>> subset of T*, in which case the set of terminals T is the vocabulary.
>> The set of non-terminals N is only needed when one wants to define a
>> general rewriting system from a grammar to define the language L.
>> Different grammar specs of L may lead to different N.
>
> Yes, good point. However, if one is trying to be clear, one needs to
> be clear as to what means by Vocabulary, V = VN U VT or just VT.
> Since, if I recall correctly, the original poster, Ralph Boland, was
> interested in a case where he has both terminals and non-terminals and
> he wanted a name for a set of just the terminals. Well, at least
> that's how I interpreted his question.
>
> The question goes back to whether there is a good one-word name for
> "the set of terminals" in a language.


How about the "terminals"? :-)


> While I like vocabulary as a
> term for describing it, I think it may be non-standard, especially in
> a context where there are non-terminals of interest.
>
> Of course, it goes the other way too, if you use vocbulary for VT,
> what word do you use for VN U VT? I don't think there is a common
> word thet means all the words and phrases in a language (VT are the
> named "words" and VN are the named "phrases" to my mind).


They will be vocabularies for different languages. The language L that
is a subset of T* is the set of sentences one would write. The language
that is a subset of (N V T)* but not T* is the grammar description
language. The subset when all variables (non-terminals) have been
expanded into constants (terminals) is L.


      Hans

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