ipython/ipython — pull request #6989 by SylvainCorlay (2014-11-19 20:09:18+00:00)
Title: Remove comparisons in traitlet links and directional links

`traitlets.link` and `traitlets.directional_link` were making comparisons of traitlet values.

The problem is that this does not work with things like numpy arrays or pandas data frames.

Another method would have been to provide an optional predicate, but in fact, I don't quite see the point of comparing the values.