Stefano Crocco wrote:
> How are you supposed to know that to_yaml is not in ruby core but in the
> standard library? I don't really know. When I started using ruby some years
> ago, I downloaded a version of the rdoc documentation from
> www.ruby-doc.org which only included documentation for the core classes (that
> is, those you can use without need to require some files), while documentation 
> for the standard library was in a separate package. Unfortunately, the
> documentation you can find nowadays includes both core and standard library.

The ri command shows the documentation for the merged core and standard 
libraries. It's sad but it's true. However, it isn't hard to find out 
what's the the core and what isn't.

This link http://www.ruby-lang.org/en/documentation/ has a link to the 
top-level www.ruby-doc.org as well as individual links to the core and 
standard API sections of ruby-doc.

When I go to www.ruby-doc.org right now, the documentation for the Core 
API is clearly separated from the documentation for the Standard API. 
The yaml library is documented in the Standard API documentation.

When I view the online (first edition) version of _Programming_Ruby_ 
(http://www.ruby-doc.org/docs/ProgrammingRuby/) the core API is 
documented in the "Built in Classes and Methods" chapter. The Standard 
library is documented in the "Standard Library" chapter. The yaml 
library isn't documented in that book because it didn't exist when the 
first edition was written. The 2nd edition (pay for) includes yaml in 
the Standard Library chapter. There is also a short tutorial about yaml 
in the marshalling chapter.

-- 
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RMagick 2: http://rmagick.rubyforge.org/rmagick2.html