Bug in fixed_point?!

[C Barrington-Leigh]

I cannot figure out what I'm doing wrong. The following does not
return a fixed point:


from scipy import optimize
xxroot= optimize.fixed_point(lambda xx: exp(-2.0*xx)/2.0, 1.0,
args=(), xtol=1e-12, maxiter=500)
print ' %f solves fixed point, ie f(%f)=%f ?'%
(xxroot,xxroot,exp(-2.0*xxroot)/2.0)

Chris