Concat and zip

[Brian Goetz]

> In defense of zip: I think it is fairly important.  Ease of expression
> (and productivity) are still the most valuable benefits of new features,
> and zip is important for a class of problems.  zip exists in Python,
> Scala, and Groovy (as "transpose" method), to name a few.

Yes, that's all good.  My worry is that the idiom doesn't transport 
well, and users will end up having a bad experience?