You're probably looking for this: http://www.drdobbs.com/blog/archives/2008/03/invariant_strin.html;jsessionid=W4D43VWK24ALLQE1GHPSKH4ATMY32JVN?print=true
Unfortunately Dr Dobb's admins decided it'd be a good idea to just kill all the links in existence. There's plenty of dead links pointing to that website. Here's a list of some other Walter's posts: http://www.drdobbs.com/blog/bioPages/author/WalterBright/index.jhtml;jsessionid=W4D43VWK24ALLQE1GHPSKH4ATMY32JVN
