From: Gregory Brown <gregory.t.brown@...>
Date: 2008-07-31T02:28:09+09:00
Subject: Suggestions for improving a trivial tag parser

Hi folks,

I need to take strings that have embedded <i> and <b> tags and split
them out into an array.
Here are some examples:

# No need to ensure valid pairs, just need to break out tags from the text
#----------------------------------------------------------------------------------------------

describe "Inline style parsing" do
  it "should return an identical string if inline styles are not detected" do
    create_pdf
    @pdf.parse_inline_styles("Hello World").should == "Hello World"
  end

  it "should return an array of segments when a style is detected" do
    create_pdf
    @pdf.parse_inline_styles("Hello <i>Fine</i> World").should ==
      ["Hello ", "<i>","Fine", "</i>", " World"]
  end

  it "should create an array of segments when multiple styles are
detected" do
    create_pdf
    @pdf.parse_inline_styles("Hello <i>Fine <b>World</b></i>").should ==
      ["Hello ", "<i>", "Fine ", "<b>", "World", "</b>", "</i>"]
  end
end

###

I fear my implementation (below) is showing one of my weakest areas in
Ruby, and probably even has some unforeseen problems.  I'm sure it can
be done more accurately in less code.  Any kind RubyTalk folks want to
school me?

###

      def parse_inline_styles(text) #:nodoc:
        require "strscan"

        sc = StringScanner.new(text)
        output = []
        last_pos = 0

        loop do
         if sc.scan_until(/<\/?[ib]>/)
           pre = sc.pre_match[last_pos..-1]
           output << pre unless pre.empty?
           output << sc.matched
           last_pos = sc.pos
         else
           output << sc.rest if sc.rest?
           break output
         end
        end

        output.length == 1 ? output.first : output
      end

###

Thanks,
-greg