[julia-users] Elegant way of dealing with evaluating on branch cuts of sqrt(z-1).*sqrt(z+1) ?

[Sheehan Olver]

For z < -1 the branch cuts cancel and the function should be equivalent to 
-sqrt(z^2-1)  (the only non-removeable branch cut is along [-1,1]), but in 
Julia it is not defined.  I'm wondering if there is a special function in 
Julia that can take care of this, or is the only solution to write my own 
(with special handlers for Arrays, etc.)?