unique expressions

[Ben Sapp]

How can I make an expresion unique?   That is, I want it to copy the
thing it references not just increment the reference.  I envision
something like the following pseudocode:

symbol x("x");
ex a = pow(x,2)+2*x+1;
ex b = a; // make b reference the same thing as a
b.make_unique();  // make a new copy of a and reference it with b.  

Thanks.  

-- 
Ben Sapp                         Los Alamos National Laboratory
email: <mailto:bsapp at lanl.gov>   Phone: (505)667-3277
Fax:   (505)665-7920             URL:   http://www.neutrino.lanl.gov/
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