Homebrew is a popular package manager for OS X, one which I use extensively. Sometimes, while upgrading the libraries, it's possible that the new library fails to work and you need to switch to using the older version. This post will describe how to do that.
In my case, I upgraded the boost library from 1.59 to 1.60. The Point Cloud Library (PCL) which depends on boost started failing with this new version and hence I had to switch it back to 1.59. After some search, we found that "brew switch" will do the trick. Here is the command: