[ragel-users] Bug? Backslash-escapes not escaped enough in .dotfiles?

[Austin Hastings]

Sure. I think this is a "dotty" bug, though.

I start with this .ragel file:

%%{
     machine test;
     ws = 0x20 | 0x09 | 0x0A ;
     action ws_act { }
     main := ( ws @ws_act )+;
}%%

Which produces this .dot file:

digraph test {
         rankdir=LR;
         node [ shape = point ];
         ENTRY;
         en_1;
         node [ shape = circle, height = 0.2 ];
         node [ fixedsize = true, height = 0.65, shape = doublecircle ];
         2;
         node [ shape = circle ];
         1 -> 2 [ label = "'\\t'..'\\n', SP / ws_act" ];
         2 -> 2 [ label = "'\\t'..'\\n', SP / ws_act" ];
         ENTRY -> 1 [ label = "IN" ];
         en_1 -> 1 [ label = "main" ];
}

I was then viewing it with the "dotty" tool, part of Graphviz. I got the 
image captured in the attached file (ragel-dotty.png). You'll notice 
there are no backslashes before 't'.

Next I tried to generate the png directly with:

     dot -Tpng -o ragel-dot.png ragel.dot

But that png file, also attached (ragel-dot.png), contains backslashes. 
Apparently, this is a "dotty" bug, since two of their tools are 
producing different results. It's definitely not a ragel issue.

=Austin


On 3/27/2011 7:14 AM, Josef Göttgens wrote:
> Hi Austin,
>
> I guess your example shows part of a .dot file. Backslashes are 
> regarded by dot and friends as escape chars, i.e. in order to print \t 
> you need to have \\t in your dot file. Whether you surround \\t with 
> single quotes or not doesn't matter.
>
> I am not sure whether you need to be concerned about this because 
> calling Ragel with the option -Vp takes care of proper escaping when 
> needed.  Could you publish you .rl file to see what you are trying to do?
>
> jg
>
>
> -----Ursprüngliche Nachricht----- From: Austin Hastings
> Sent: Sunday, March 27, 2011 12:04 PM
> To: ragel-users at complang.org
> Subject: [ragel-users] Bug? Backslash-escapes not escaped enough in 
> .dotfiles?
>
> Howdy,
>
> I'm poring over some .dot files, trying to understand what's wrong with
> my tokenizer. And I'm on Windows (XPpro, sp3, en-us), which means that
> my stuff probably doesn't work like anyone else's.
>
> I can see the .dot file contains labels generated like '\\t'  (that's
> apos-backslash-backslash-tee-apos).
>
> But dotty is suppressing the backslash, for some reason.
>
> If I change them to 4 slashes:  '\\\\t' then I see one slash in the
> dotty window.
>
> Is this a ragel bug (not generating the right number of slashes) or a
> dotty bug (ignoring too many slashes) ?
>
> For example:
>
>     2 -> 2 [ label = "'\\t', '\\f'..'\\r', SP / whitespace_act,
> buffer_input" ];
>     2 -> 2 [ label = "'\\n' / newline_act, whitespace_act, 
> buffer_input" ];
>
> =Austin
>
>
> _______________________________________________
> ragel-users mailing list
> ragel-users at complang.org
> http://www.complang.org/mailman/listinfo/ragel-users
>

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