From: Phrogz <gavin@...>
Date: 2007-02-09T01:35:08+09:00
Subject: Re: Ruby as a configuration language

Tapio Kelloniemi wrote:
> I wish I could write the profiles in Ruby to avoid
> creating yet another advanced configuration language.

Some people will suggest YAML. That's certainly a reasonable way to
go. Don't create your own config language when a simple markup exists
that translates painlessly into Ruby data structures.

> # An example package description file. The actual building commands are
> # written in a bash script.
> name = "gcc"
> version = "4.1.1"
> title = " "GNU Compiler Collection"
> description = "..."
>
> archive {
>     localname = "#{name}-#{version}.tar.bz2"
>     originalname = "#{name}-#{version}.tar.gz"
>     baseurl "ftp://ftp.gnu.org/gnu/gcc/#{version}/"
>     baseurl "ftp.mirror.site/gnu/gcc/#{version}/"
>     convert = "gz-bz2"
> }
>
> # Optional components
> feature "gfortran" {
>     title = "Fortran compiler"
>     depend "gmp"
> }
>
> ### END example

If you want a true DSL, here's some untested code pointing you in the
right direction. I have no idea if you can have more than one archive,
or more than one feature, or more than one baseurl per Archive...but
you can do it.

class Archive
  attr_accessor :localname, :originalname, :baseurl, :convert
end

class Feature
  attr_accessor :title, :dependency
  def depend( depends_on )
    @dependency = depends_on
  end
end

def archive( &block )
  $archive = Archive.new
  $archive.instance_eval( &block )
end

$features = []
def feature( &block )
  f = Feature.new
  $features << f
  f.instance_eval( &block )
end