From: Ilias Lazaridis <ilias@...>
Date: 2005-03-25T12:59:49+09:00
Subject: Re: [EVALUATION] - E03 - jamLang Evaluation Case Applied to Ruby

Martin DeMello wrote:
> Ilias Lazaridis <ilias@lazaridis.com> wrote:
> 
>>The above thread showed finally the need to split the evaluation down
>>into smaller chunks.
>>
>>Here is a simple evaluation template (first part) which can be applied 
>>to the Ruby language:
>>
>>http://lazaridis.com/case/lang/index.html
> 
> Okay, that's a neat bit of work. Here's a quick solution (ruby makes
> most of this fairly trivial):
> 
> # here's your basic talker class
[...]

preliminary draft:

http://lazaridis.com/case/lang/ruby.html

> # reflection
> class Talker
> 
>   # simple
>   
>   def sayYourClassName
>     puts self.class.name # the 'self' is optional here
>   end

omitting "self" (puts class.name) leads to an error

>   # objects know nothing about the variables that are bound to them
>   # (a variable name is not the name of the instance anyway). The
>   # closest you can come to the "name" of an object is it's object id, so...
>   def sayYourInstanceName
>     puts object_id # again, you could say self.object_id if you prefer
>   end

ok

>   # advanced
>   
>   # caller returns a stack (array) of strings of the form 
>   #   file:linenumber in `method'
>   # so we extract the most recent one and parse the method name out
>   # code from PLEAC
>   def thisMethodName
>     caller[0] =~ /in `([^']+)'/ ? $1 : '(anonymous)';
>   end

I understand the concept.

is there possibly a more direct solution available, with cleaner code 
and a stable/higher execution speed?

>   # string interpolation in action - the bit between the #{} can be
>   # any valid expression; to_s will be called on the result and 
>   # interpolated into the string
>   def sayHelloAdvanced
>     puts "#{thisMethodName}: Hello World"
>   end

ok

>   # expert
>   def sayYourClassDefinition
>     puts "Class:"
>     sayYourClassName

     puts "Class #{self.class.name}" >> Class Talker

but

     puts "Class #{sayYourClassName}" >> Talker Class
     puts "Class " + sayYourClassName.to_s >> Talker Class

why?

>     # %{} is another way to write a string literal

#{} - inside strings
%{} - outside of strings

>     # (looks neat for multiline strings)
>     # we use the standard 'inspect' method to print out arrays of 
>     # method names in a ["meth1", "meth2", ...] format
>     puts %{
> Methods:
>   public:
>     #{public_methods.inspect}
>   protected
>     #{protected_methods.inspect}
>   private:
>     #{private_methods.inspect}
>   non-inherited:
>     #{(methods - self.class.superclass.instance_methods).inspect}
>       
>   Instance Variables:
>     #{instance_variables.inspect}
>     }

Can I get somehow a more precise reflection of the class definition 
(output similar to the original class-def, excluding code)?

>     # note that the instance variables belong to the *instance*, not
>     # to the class, so they're not technically part of the class
>     # definition. the following code is illustrative:
>     #
>     # class A
>     #   attr_accessor :foo, :bar # defines getters and setters
>     # end
>     #
>     # a = A.new
>     # p a.instance_variables # => []
>     # a.foo = 10
>     # p a.instance_variables # => ["@foo"]
>     # b = A.new
>     # p b.instance_variables # => []
>   end

ok

>   def sayYourClassCode
>     puts "Sadly, you cannot introspect the source code from within a program"
>     # though see http://rubyforge.org/projects/parsetree/
>     # for a way to get at the parsed AST
>   end 

ok

> end
> 
> # testing it out
> 
> if __FILE__ == $0
>   talker.sayHelloAdvanced
>   talker.sayYourClassName
>   talker.sayYourClassDefinition
>   talker.sayYourClassCode
> end
> 
> Hope this helps.

very much!

thank you for your efforts.

> martin

..

-- 
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