Collaborative collection of useful userRPL snippets

[pier4r]

So here some questions (rephrased) that I find interesting from the facebook group (see also http://www.hpmuseum.org/forum/thread-9679.html )

TODOs
- How do you sort a matrix by column (define a sort metric that for you makes sense) or by row?

- by extension, any other matrix/vector operations that you find useful not present in the base RPL library?