Re: On % being a valid first character in a content line

On Sat, 2009-06-13 at 10:33 -0700, Joshua Choi wrote:
> I see! Thank you for the reply.
> 
> Now regarding document indicators, is the ... document end marker  
> *required* for separating a document's content from a document with  
> directives?


Yes. 9.2 states:

---
A YAML stream consists of zero or more documents. Subsequent documents
require some sort of separation marker line. If a document is not
terminated by a document end marker line, then the following document
must begin with a directives end marker line. [[so, no directives]]
...

> I was kind of confused on how directives factored into the flexible  
> parsing of YAML streams. I assumed that ... was completely optional  
> and that a % directive line could start a new document, without a ....  
> But it would make sense if the ... would be required, or else in the  
> example "%YAML 1.2" would be interpreted as part of the plain scalar  
> "Blah blah blah". Is this so?

Yes. 9.1.2 states:

---
Using directives raises a potential ambiguity. It is valid to have a “%”
character at the start of a line (e.g. as the first character of a
top-level mapping key) [[This is the phrase that you detected was wrong;
but as I have shown there are other cases]]. How, then, to distinguish
between an actual directive and a content line that happens to start
with a “%” character? 

The solution is the use of two special marker lines to control the
processing of directives, one at the start of a document and one at the
end. 

At the start of a document, lines beginning with a “%” character are
assumed to be directives. The (possibly empty) list of directives is
terminated by a directives end marker line. Lines following this marker
can safely use “%” as the first character. 

At the end of a document, a document end marker line is used to signal
the parser to begin scanning for directives again. 
...

The whole thing was a mess in 1.1 and this hopefully cleaned it up
(well, except for considering % as an indicator which I will fix today,
and hopefully lay it to rest once and for all :-).

Have fun,

	Oren Ben-Kiki


------------------------------------------------------------------------------
Crystal Reports - New Free Runtime and 30 Day Trial
Check out the new simplified licensing option that enables unlimited
royalty-free distribution of the report engine for externally facing 
server and web deployment.
http://p.sf.net/sfu/businessobjects
_______________________________________________
Yaml-core mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/yaml-core