From: Joel VanderWerf <vjoel@...>
Date: 2003-01-24T03:59:48+09:00
Subject: Re: emulating C preprocessor's #if

Yuri Leikind wrote:
> Perhaps I might have misunderstood the main point of your letter, but I
> think Ruby is dynamic enough to do what you want without any other
> changes in the core language:
> 
> module M
> 
>    def M.print_platform
>       print "Platform is..." + M.platform_dependent_code() + "\n"
>    end
> 
>    case RUBY_PLATFORM
>    
>       when /solaris/i then
>          def M.platform_dependent_code
>             "Solaris"
>          end
>       when /linux/i then
>          def M.platform_dependent_code
>             "Solaris"
>          end
>       when /win/i then
>          def M.platform_dependent_code
>             "Solaris"
>          end
>       else
>          def M.platform_dependent_code
>             "unknown"
>          end
>      end
> end
> 
> M.print_platform

My example was too simple :)

I'm thinking of a case where platform-dependent code is mixed with 
independent code and hard to factor out without making a lot of extra 
method calls. Also, if you have more variables than just platform, you 
get combinatorial explosion if you have to write a separate method for 
each possibility. My suggestion is a last resort...