From: VardhanVarma@...
Date: 2000-10-17T11:49:58+09:00
Subject: [ruby-talk:5621] [RRFC] versioning revisited


       Here is my little idea,
       i won't stand for it though

hipster writes:
 > 
 > 1. Version check syntax
 > 
 > ruby version
 >   require "1.6"               # at least 1.6
 
 Instead of numeric version number what about 'features'
 e.g.
        require "thread" supporting "pre-emption" ?
        Of course it can also be
        require "ruby" supporting "1.6" 


 > 2. How libraries (can) specify their versions
      
        supports "pre-emption";
        supoprts "1.6"

 > for binary libraries (*.so), every .so implements (e.g.):
 >   char* library_version(){
 >     return "4.2";
 >   }
        
        .so's are best loaded thru a .rb, which does all the check,
        and loads and binds .so functioncs. This way, .rb can select
        a proper implementation ( e.g. of a fractal.so is loaded in
        multi-threaded or uni-threaded enviroment.
        e.g.
        1.
        require "fractal" supporting "multi-threaded"
                -- fractal.rb loads fractal.so, and aliases
                              Fractal.draw to fractal.so/draw-multi
        2.                             
        require "fractal" supporting "mono-threaded" 
                -- fractal.rb loads fractal.so, and aliases
                              Fractal.draw to fractal.so/draw-uni
        
 > 2.1 A more fine-grained scheme

   IMHO class-level-thing will be a _bad_ idea, still for
   completeness:

       clas Foobar [ << Inherits ] 
            supports "foo","bar"

 > 
 > AFAICS the above scheme does not collide with the current versionless
 > requires and libraries.

   (-;

           
 > If there are multiple versions of the same library present in the search
 > path, they are all tried until a match is found. If no library matches the
 > first on the path is loaded (with a warning?). <uneasy feeling>

         But to check the version, you have to load a library, which
may do something bad ( setting a variable at top level ), and then you
load next library which may do more bad ( check that variable to see
if already loaded !!! ).

           IMHO, you'll have to run a 'indexer' on library, which will
generate a neat little table:

library -- version -- physical_path --


           This will also reduce 'magic', and fast up loading a
little.



        
 > 
 > 

-- 
Vardhan Varma <vardhan@cadence.com>  +91-118-4562842 Extn / VMail: 4123
Random Quote: The only thing you take with you when you're gone 
is what you leave behind.    -John Allston