From: "Ara.T.Howard" <Ara.T.Howard@...>
Date: 2005-09-12T03:28:49+09:00
Subject: Re: r4 - the simplest ruby pre-processor

On Sun, 11 Sep 2005, Christian Neukirchen wrote:

> "Ara.T.Howard" <Ara.T.Howard@noaa.gov> writes:
>
>> all this talk about pre-processors and erb got me thinking : what would it
>> take to code up a ruby pre-procssors that could be used for any laguange.  my
>> first crack is 38 lines of ruby that pre-process any files on the command line
>> (or stdin) using ruby as the macro language and a convenience function 'macro'
>> which can be used to define ruby methods which return test that is used as
>> output.  functions declared this way need not do any explicit io.
>
> Alternative implementation ("r5"):
>
>    def macro(name, &block)
>      Kernel.send(:define_method, name) { |*args|
>        puts block.call(args)
>      }
>    end
>
>    send(($DEBUG ? "puts" : "eval"), ARGF.readlines.map { |line|
>      if line[0] == ?|
>        line[1..-1]
>      else
>        "puts #{line.chomp.dump}\n"
>      end
>    }.join)
>
> Happy hacking,

a version which optionally interpolates - six lines, ergo r6

     harp:~ > cat in
     | x = 42

     using the -i switch i can interpolate x as #{ x }


     harp:~ > r6 in

     using the -i switch i can interpolate x as #{ x }


     harp:~ > r6 --interpolate in

     using the -i switch i can interpolate x as 42


     harp:~ > cat r6
     #! /usr/bin/env ruby

     def macro(m, &b); Kernel::send('define_method', m){|*a| puts b.call(a)}; end

     debug = $DEBUG || ENV['DEBUG'] || ARGV.delete('-d') || ARGV.delete('--debug')

     interp = $INTERPOLATE || ENV['INTERPOLATE'] || ARGV.delete('-i') || ARGV.delete('--interpolate')

     meth = debug ? 'puts' : 'eval'

     src = ARGF.readlines.map{|l| l =~ %r/^\s*\|(.*)/ ? $1 : (interp ? "puts \"#{ l.chomp }\"" : "puts #{ l.chomp.dump }")}

     send meth, src.join("\n")

cheers.

-a
-- 
===============================================================================
| email :: ara [dot] t [dot] howard [at] noaa [dot] gov
| phone :: 303.497.6469
| Your life dwells amoung the causes of death
| Like a lamp standing in a strong breeze.  --Nagarjuna
===============================================================================