title: Problems installing rdoc, irb, bluecloth, chronic on fedora 12
body: <p>What do these errors mean?</p>
  
  <pre><code>[root@localhost config]# gem install bluecloth
  Building native extensions.  This could take a while...
  ERROR:  Error installing bluecloth:
      ERROR: Failed to build gem native extension.
  
  /usr/bin/ruby extconf.rb
  can't find header files for ruby.
  
  
  Gem files will remain installed in /usr/lib64/ruby/gems/1.8/gems/bluecloth-2.0.7 for 
  inspection.
  Results logged to /usr/lib64/ruby/gems/1.8/gems/bluecloth-2.0.7/ext/gem_make.out
  [root@localhost config]# 
  </code></pre>
  
  <p>And this</p>
  
  <pre><code>[root@localhost config]# gem install chronic
  Successfully installed json_pure-1.4.3
  Successfully installed rubyforge-2.0.4
  Successfully installed hoe-2.6.0
  Successfully installed chronic-0.2.3
  4 gems installed
  /usr/lib64/ruby/gems/1.8/gems/rdoc-2.5.8/lib/rdoc/ruby_lex.rb:67: warning: 
  parenthesize argument(s) for future version
  ERROR:  While executing gem ... (Gem::DocumentError)
      ERROR: RDoc documentation generator not installed: no such file to load -- irb/slex
  [root@localhost config]# 
  </code></pre>
  
  <p>I have installed rdocs using "yum install ruby-rdocs". But I don't understand what this error means</p>