From: Caleb Clausen <vikkous@...>
Date: 2008-10-26T08:02:09+09:00
Subject: Re: regular expressions and conditionals

On 10/25/08, Matt Harrison <iwasinnamuknow@genestate.com> wrote:
> I'm writting a little program to convert some source files to html.
>
> I'm using regexp's to determine the content of each line and format it
> accordingly. For example, if the line starts with a #, then it should be
> output with a div (and id set to 'comment').
>
> The problem is with matching the regular expressions. If I do this:
>
> f = File.new("myfile", "r")
> while !f.eof?
>   line = f.gets
>
>   if line.match(/^# (.*)/)
>     puts "<div id='comment'>#{line.match(/^# (.*)/)[0]}</div>"
>   end
> end
>

I think what you're trying to write is a little more like this:
f = File.new("myfile", "r")
while line = f.gets
  if line.match(/^# (.*)/)
    line="<div id='comment'>#{line.chomp}</div>\n"
  end
  puts line
end

> Then not only do I get the commen lines formatted properly, I also get a
> "nil" for every other line in the file.

I didn't see any nils when I ran it... it just didn't print anything
but comments. Which would be because your original only printed lines
back out if they matched your comment pattern.

Why do you have a space after the # in your pattern? I've found it to
be good luck to always escape # when in regexps, even if it isn't
followed by a {. Probably a bug lurking in there.