From: "wbsurfver@..." <wbsurfver@...>
Date: 2007-11-29T11:50:06+09:00
Subject: Re: I get syntax errors from RDParser example I found on internet

On Nov 28, 5:04 pm, yermej <yer...@gmail.com> wrote:
> On Nov 28, 2:59 pm, "wbsurf...@yahoo.com" <wbsurf...@gmail.com> wrote:
>
>
>
> > =begin
> > I got this recursive decent parser from:http://www.rubyinside.com/recursive-descent-parser-for-ruby-300.html
>
> > I get this syntax error:
> > C:/rb-play/parser/try.rb:13: syntax error, unexpected ']', expecting
> > kEND
> >   g.operation           /[+-*/]/
>
> > if I change that line to:
> >   g.operation           /[+-]/
> > that line no longer has an error, so the / and * threw it off
>
> > then I get an error on another line:
>
> >   g.string              %r(["'](.*?[^\]|.*?)["'])
> > C:/rb-play/parser/try.rb:15: warning: character class has `[' without
> > escape
> > C:/rb-play/parser/try.rb:15: unmatched (: /["'](.*?[^\]|.*?)["']/
>
> In the first, you need the - at the beginning of the (or escaped with
> a backslash) or Ruby interprets it as a character range. You also need
> to escape the first forward slash or Ruby interprets it as the end of
> the Regex. So:
>
> /[-+*\/]/
>
> In the second, the backslash needs to be escaped. If it isn't, then it
> is used to escape the following ] so the character class isn't closed
> until the final ] which is just wrong. So:
>
> %r(["'](.*?[^\\]|.*?)["'])
>
> Consider both issues were due to missing backslashes, they were
> probably originally correct. I guess somewhere along the way the
> backslashes were interpreted as escape characters and didn't make it
> to the final page.
>
> Jeremy

That first one I had tried before and it didn't work, but if I move
the * to the begining it does work:
/[*+-\/]/