[L2Ork-dev] test out [unpost] please

[Jonathan Wilkes]

Hi all,

I'm relying a lot on [unpost] in the regression tests, so I'd like
people to test out [unpost] to see if it has any bugs.

You send it an input and it forward it to its right outlet.

Now if anything downstream from its right outlet triggers an error,
[unpost] will catch it and send it as a symbol to the left outlet.

This way I can check for things like the existence of methods, and
route a more meaningfully structured message to the testing
infrastructure for the regression tests.

The object was originally implemented by matju for desiredata. I
changed the outlet ordering (I like it better that the first thing
guaranteed to be output is from the right outlet). I also fixed a
crasher with recursion and another issue that made it too easy for the
user to get stuck in a confusing situation where [unpost] could still
capture all the output. Finally, I gave it an "error" argument in case
the user wants only to intercept error messages.

Best,
Jonathan