<blockquote>
  <p><strong>Possible Duplicate:</strong><br>
  <a href="https://stackoverflow.com/questions/13537/bootstrapping-a-language">Bootstrapping a language</a>  </p>
</blockquote>



<p>What's the importance of having an interpreter for a given language written in the target language (for example, <a href="http://en.wikipedia.org/wiki/PyPy" rel="nofollow noreferrer">PyPy</a>)?</p>

I'm sure there are many different reasons for doing it. In some cases, it's because you truly believe the language is the best tool... so writing the language interpreter or compiler in the language itself can be seen as a form of dogfooding. If you are really interested in this subject, the following article is a really amazing read about the development of squeak. The current version of squeak is a smalltalk runtime written in smalltalk.
http://users.ipa.net/~dwighth/squeak/oopsla_squeak.html