From: Paul Smith <paul@...>
Date: 2009-09-23T19:23:52+09:00
Subject: Re: Mini Parser

On Wed, Sep 23, 2009 at 10:55 AM, Karthikeyan Balasubramanian
<karthikb@mobilink.com.kw> wrote:
> Hi all,
>
>  I have a requirement.  I have a to read some commands from file and
> output as another file.  For example if the input file is like below:
>
> 6
> WRITE  Today
> WRITE  is
> UNDO  1
> WRITE  my
> UNDO  2
> WRITE birthday
>
> Output file will be like this.
>
> Today is birthday
>
> WRITE basically write's string after the command and UNDO will undo N
> number of line preceding it.  Complexity here is last UNDO has to UNDO
> the previous undo's work.
>
> So far I have been able to only come up with the below code:
>
> begin
>  file = File.new("abc.txt", "r")
>  while (line = file.gets)
>    line.grep(/WRITE/) { |s|
>      puts s
>    }
>  end
>  file.close
>
> rescue => err
>  puts "Exception: #{err}"
>  err
> end
>
> Any help here?
> --
> Posted via http://www.ruby-forum.com/.
>
>

If you want undoable commands you need to keep a command history.  I'd
check out the Command design pattern if I were you.

-- 
Paul Smith
http://www.nomadicfun.co.uk

paul@pollyandpaul.co.uk