Lawrence D'Oliveiro <l...@geek-central.gen.new_zealand> writes: > In message <mailman.608.1288889032.2218.python-l...@python.org>, Robert Kern > wrote: > > So examining LHS "selectors" is not sufficient for determining > > immutability. > > Yes it is. All your attempts at counterexamples showed is that it is not > necessary, not that it is not sufficient.
You've got them the wrong way around. A is sufficient for B if and only if B is true whenever A is true; i.e., it is never the case that A is true and B is false. In this case, we also say that B is necessary for A. See also http://en.wikipedia.org/wiki/Necessary_and_sufficient_condition -- [mdw] -- http://mail.python.org/mailman/listinfo/python-list
