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Comments on Understanding "de Morgan's laws"
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Understanding "de Morgan's laws"
While trying to understand logical 'or'/'and', I encountered another problem (I'm writing Python code here, but my question is about the logic, not about any given programming language). I have some code like:
if x or y:
pass
else:
do_something()
(Of course, following the other Q&A, I made sure that the real x and y make sense independently as conditions.)
I wanted to focus on the else case, because it's actually interesting. I figured out that I could negate the condition to flip the cases, and then the else: pass part would be unnecessary:
if not(x or y):
do_something()
However, other obvious attempts did not work:
if not x or y:
do_something()
if not x or not y:
do_something()
if (not x) or (not y): # not even with more parentheses!
do_something()
I asked about this elsewhere and was told it had something to do with "de Morgan's laws". What does this mean? Can I use these "laws" to understand how to write the code correctly? How exactly do they apply?
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