From: Robert Klemme <bob.news@...>
Date: 2004-09-15T20:24:50+09:00
Subject: Re: Recursive Objects (Arrays) in Ruby


"Wandering Mango" <drxpxbxx@wxxoevxer.xoxm> schrieb im Newsbeitrag
news:slrnckegn0.q4u.drxpxbxx@octothorpe.local...
> On 2004-09-14, Robert Klemme <bob.news@gmx.net> wrote:
> >
> > "Wandering Mango" <dropbox@whoever.com> schrieb im Newsbeitrag
> > news:ci5q1d$a9b@odah37.prod.google.com...
> >> As a disclaimer, I'm new to object-oriented programming and to Ruby;
so
> >> I'm not sure if I'm even describing this problem correctly. Here
goes:
> >>
> >> I have an object called "formula" which has properties .string (the
> >> original formula), .leftSub, .rightSub (left and right subformula of
> >> the original formula) and .characterType (an array identifying each
> >> character in .string as being a particular type - e.g., number,
letter,
> >> and so on).
> >
> > Assaph answered your problem question, but I'd like to raise another
> > question: this looks like an expression tree - possible as outcome of
a
> > parse stage.  It seems to me that the more appropriate storage would
be
> > (besides the original string) a sequence of tokens per node.
>
> Thank you.  Your analysis is quite perceptive: that is excatly where I
> am headed.  I'm parsing the original string into substrings, and then
> doing the same to them until I get to atomic strings.  But if there
> is a better way to do this, I'm more than willing to entertain it -
> could you tell me a litle bit more about what "a sequence of tokens
> per node" is?  I googled the phrase, but am not exactly sure what
> I am looking for.  Thank you.

You should probably use a parser generator such as
http://raa.ruby-lang.org/project/racc/ and
http://raa.ruby-lang.org/project/ruby-yacc/ You'll finde more on the RAA
here: http://raa.ruby-lang.org/search.rhtml?search=parser (look out for
parser generators).

You can find more with Google:
http://www.google.com/search?q=%22parser+generator%22+ruby

If you search for "parsing theory" you'll find quite some resources on the
matter.  The classical book about the issue is this:
http://www.amazon.com/exec/obidos/tg/detail/-/0201101947

Kind regards

    robert