From: Sam Kong <sam.s.kong@...>
Date: 2006-12-21T10:14:48+09:00
Subject: Re: Regex question: this should be easy but doesn't work as I expect.

Hi Carlos,

Carlos wrote:
> Hi. The problem is that you can very easily NOT match "three" even if it's
> there. I mean, if you have
>    /1.*3?.*5/ =~ '12345'
>
> the engine can succeed matching the 1 at the beginning, the 5 at the end,
> and trying to match the 3 where the 4 is... and failing, but since it's
> optional, the overall match succeeds.
>
> I think you should try it in two steps: first, try to match with the 3; if
> that fails, without the "3". Something like:
>
>  /(?:(1).*(3)|(1)).*(5)/
>
> (The '1' will come either on the first or third array position, you'll have
> to take care of that.)

Yes, you understand exactly what my problem is.
Actually I guessed it as you said even if I couldn't explain it as well
as you did.
The solution I found was using 2 regexes.
First, I try to find a match assuming "three" is there.
If it fails, I try to find a match without "three".
This solved my problem.
But I wanted to know that if there's a one-shot solution.

This is the actual problem, just in case someone wants to know.

html = <<END
<tr id="row2_210819526">
    <td class="year">
        <h5>2004 Used</h5></td>
    <td class="carlink"><h5>

            <a name="210819526" href="210819526.html">BMW 325Ci
            Coupe</a><br />

        </h5></td>


    <td class="mileage">

        <span class="body20">38,604<br /></span><span
class="body30">Mileage</span></td>
    <td class="price">
        <span class="body20">

                    $24,995



            <br />
        </span>


            <span class="body30">Price</span>
        </td>

    <td class="distanceFromZip">
        <div class="zip">
            <span class="body20">0 mi<br /></span><span
class="body30">from ZIP</span>
        </div></td>

        <td class="productTileCell" rowspan="2" valign="top">

            <div class="srlProductContainer">




            </div>


        </td>

</tr>
<tr id="row3_210819526">
    <td class="left">

                <a href=210819526.html><img
src="http://images.autotrader.com/images/2006/10/16/210/819/1092478286.210819526.IM1.MAIN.60x45_A.60x45.jpg"
border="0" bordercolor="#000000" width="60" height="45"></a>&nbsp;

                <div class="body40" style="padding-bottom:3px">
                        <img
src="http://www.autotrader.com/img/fyc/icn_camera_17x17.gif"
alt="Actual Photo Available" width="17" height="17" border="0"
/>&nbsp;9 Photos
                    <br />
                </div>




        <img src="http://www.autotrader.com/img/blank_dot.gif"
width="60" height="1" /></td>
    <td class="center" colspan="2">
        <div class="centerinfo">


                    <p class="color body20">Color - Mystic Blue
Metallic</p>


                <p class="description">Dark Blue/Beige, Premium Pkg,
Xenon Light, Single Compact Disc, Dual Power Seats, Memory Seat, Still
under Free BMW Maintenance and 4yr/50k Factory...</p>


                    <p class="vin">VIN WBABV13454JT20104</p>





                <div class="body40" style="padding-top:5px;"><a
name="210819526" href="210819526.html">View Car Details</a><br /></div>


        </div></td>
    <td>&nbsp;</td>
    <td valign="top" class="right body30">




        <p class="dealername">



                <a name="210819526" href="210819526.html">null</a>
                <br />


        </p>








        <br />

    </td>
</tr>
END

def parse_row row
  m = row.scan(/.+?<h5>(\d{4}) Used<\/h5>.+?<h5>.+?<a name=\"\d+\"
href=\"(\d+.html)\">(.+?)<\/a><br \/>.+?<\/h5>.+?<span
class=\"body20\">([0-9,]+)<br \/><\/span><span
class=\"body30\">Mileage<\/span>.+?(\$[0-9,]+).+?(http:\/\/[^\"]+?\.jpg).+?Color
- (.+?)<\/p>/m)
  if m[0].nil?
    m = row.scan(/.+?<h5>(\d{4}) Used<\/h5>.+?<h5>.+?<a name=\"\d+\"
href=\"(\d+.html)\">(.+?)<\/a><br \/>.+?<\/h5>.+?<span
class=\"body20\">([0-9,]+)<br \/><\/span><span
class=\"body30\">Mileage<\/span>.+?(\$[0-9,]+).+?(http:\/\/[^\"]+?\.jpg)?.+?Color
- (.+?)<\/p>/m)
  end
  m[0]
end

p parse_row(html)


Sorry about the messy code.

Thanks.

Sam