From: gwtmp01@...
Date: 2005-10-27T06:42:13+09:00
Subject: Re: Meta methods to govern meta data?


On Oct 26, 2005, at 3:32 PM, Adam Sanderson wrote:
> I think you could extend Object to define something working like this:
> comment "Doubles the number"
> params :n => "Number to be doubled"
> def double(n)
>   n * 2
> end
>

It seems to me that if you want to associate annotations with a
particular method they need to be syntactically connected to the
def/end block.  In your example there is no way to do that unless
you are proposing that comment and params etc. all become keywords.
I'd like to avoid that type of keyword explosion.

Thinking out loud...

The syntax of a method definition already has a structure that admits
to additional "clauses":

     def name(arg1, arg2)
         # body
     rescue
         # code
     ensure
         # code
     end

Why not extend this to something like:

     def name(arg1, arg2)
     notes
         comment "This is a comment"
     body
         # body
     rescue
         # code
     ensure
         # code
     end

Alternatively you could put the notes at the end to avoid
the addition of the 'body' keyword.

     def name(arg1, arg2)
         # do something
     notes
         comment "This is an example"
     end

Another variation would be to have the annotation keyword
be an alternate syntax for the start of a method definition:

     notes
         description  "This method takes two arguments"
         status       :experimental
     def name(arg1,arg2)
         # code
     ensure
         # code
     end

There  is the question of the syntax of the text between
'notes' and 'def'.  Probably best to reuse the existing
method syntax but treat the "methods" that appear between
'notes' and 'def' as no-ops.

A similar syntax could be used to annotate classes:

notes
     description "This is an annotated class"
     author      "Gary Wright"
class Sample

   notes
     "This is an annotated method"
   def foo
   end
end

For what it is worth, this is very similar to Eiffel's "indexing"
clause.

Gary Wright




Gary Wright