From: debbie@...
Date: 2005-09-10T09:11:30+09:00
Subject: Using Ruby as a preprocessor for another language

I have the misfortune of being stuck programming in a very bad
scripting language that has poor support for functions, variable
substitutions, loops, etc. etc. (It's a proprietary language called
Aegis scripting language, for scripting NPCs in a game.)

I've been using Ruby as a macro pre-processor so that I can write more
maintainable scripts without violating the DRY (Don't Repeat Yourself)
principle. Presently, I have the following functionality:

1. #{...} strings are evaluated by Ruby
2. lines starting with @ are evaluated by Ruby

Thanks to Ruby's power and simplicity, the ENTIRE pre-processor is
just these few lines:

while line = gets
        line.chomp!
        if line =~ /^\s*\@(.*)$/
                # Line starts with a @; it is Ruby code
                puts $1
        else
                # Line should be printed, with #{} substitution
available
                puts "puts \"#{line.gsub('"', '\"')}\""
        end
end

This allows me to "compile" a template like this:

        http://theanimaro.com/debbie/ruby/template.sc

into a script like this:

        http://theanimaro.com/debbie/ruby/test.sc

Now my question is, am I reinventing the wheel here in that
pre-processor code I wrote---is there already an existing module in
the RAA that does this? I didn't want to use ERuby because I find that
those <% %> <%= %> tags everywhere make the script unreadable (ERuby
is more for HTML IMO).