flipping specific bits in numeric array

les ander les_ander at yahoo.com
Sun Oct 6 19:34:57 CEST 2002

suppose i have a numeric array of 1's and 0's and i would like
to flip the 1's --> 0's for only selected entries:
for example



I_a=nonzero(a<0.5)   # I would like to flip bits for entries of "state"
                     # at index in I_a

for i in I_a:
   if state[i]==0: state[i]=1
   else: state[i]=0

is there are faster way? thanks

furthermore, is it possible to overload the "not" operator for
numeric so that the i could achieve the above with simply "not a"?

p.s. I know what numarray has array indexing, however, i don't 
want to use numarray since i am using MLab which does not seem to support 

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