hpricot：An Hpricot Showcase：Hpricot Basics：Finding Just One Element

everyday Ruby 
>> require "hpricot"
=> true
>> doc = Hpricot("<p class='posted'>A simple <b>test</b> string.</p>")
=> #<Hpricot::Doc {elem <p class="posted"> "A simple " {elem <b> "test" </b>} " string." </p>}>
>> doc.at("p")
=> {elem <p class="posted"> "A simple " {elem <b> "test" </b>} " string." </p>}
>> doc.at("b")
=> {elem <b> "test" </b>}
>> doc.at("b")['onload']
=> nil
>> doc = Hpricot("<p class='posted'>A simple <b>test</b> string.</p>")
=> #<Hpricot::Doc {elem <p class="posted"> "A simple " {elem <b> "test" </b>} " string." </p>}>
>> doc.at("p"){'posted'}
=> {elem <p class="posted"> "A simple " {elem <b> "test" </b>} " string." </p>}
>> doc.at("p"){'class'}
=> {elem <p class="posted"> "A simple " {elem <b> "test" </b>} " string." </p>}
>> doc.at("p")['posted']
=> nil
>> doc.at("p")['class']
=> "posted"
>> doc.search("//p")[0]['class']
=> "posted"
>> doc.at("p").class
=> Hpricot::Elem
>> doc.search("//p").class
=> Hpricot::Elements
>> doc.search("//p")
=> #<Hpricot::Elements[{elem <p class="posted"> "A simple " {elem <b> "test" </b>} " string." </p>}]>
>> doc.search("p")
=> #<Hpricot::Elements[{elem <p class="posted"> "A simple " {elem <b> "test" </b>} " string." </p>}]>

「//」の有無はどう影響？