On Feb 20, 2012, at 9:05 AM, ancienthart wrote:
> Guys, is there a method or function to flip an equation or inequality?
>
> I'd like to turn 2*x + 3*y < 8 into 8 > 2*x + 3*y automatically.
>
> Joal Heagney
If you just mean to reverse the order in which it is printed without changing
the mathematical meaning then the function below should work (at least for
simple cases). If you want to actually reverse the meaning then it's actually
easier since you can just use orig_op.
-Ivan
def reverse_inequality(eq):
"""
Reverse the order of the inequality without changing it's meaning.
"""
orig_op = eq.operator() # The "top-level" operator
if orig_op == operator.lt:
op = operator.gt
elif orig_op == operator.le:
op = operator.ge
elif orig_op == operator.gt:
op = operator.lt
elif orig_op == operator.ge:
op = operator.le
elif orig_op == operator.eq:
op = operator.eq
elif orig_op == operator.ne:
op = operator.ne
else:
raise TypeError, "this expression must be a relation"
return op(eq.rhs(), eq.lhs())
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