Ruby-ists:

We all know this clever idiom to turn a variable that might be an Array into
one known to be an Array:

  thing = [thing].flatten

That saves a lot of if statements to permit thing's type to overload.

What is the opposite (clever) operation? How to turn a list of one item into
one item, and a list of zero items into nil, but pass thru the list of many
items?

-- 
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 http://www.oreilly.com/catalog/9780596510657/
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