implement compare-and-swap (check-and-set, whatevs)

[slyphon]

for the concurrency-enthusiasts

set('/foo/bar', 'the new data', :check => 'the current data')

# which would do

data, stat = zk.get('/foo/bar')

if data == opts[:check]
  zk.set('/foo/bar', 'the new data', :version => stat.version)  
else
  raise CheckAndSetAssertionFailed, "You think it's '#{opts[:check]}' but it's '#{data}'"
  # yes, that's a reference to The Wire
end

with some number of :retries perhaps