boolean-logic

In [20]: print None or False -------> print(None or False) False In [21]: print False or None -------> print(False or None) None This behaviour confuses me. Could someone explain to me why is this happening like this? I expected them to both behave the same. The expression x or y evaluates to x if x is true, or y if x is false. Note that "true" and "false" in the above sentence are talking about "truthiness", not the fixed values True and False . Something that is "true" makes an if statement succeed; something that's "false" makes it fail. "false" values include False , None , 0 and [] (an

I just want to flip a boolean based on what it already is. If it's true - make it false. If it's false - make it true. Here is my code excerpt: switch(wParam) { case VK_F11: if (flipVal == true) { flipVal = false; } else { flipVal = true; } break; case VK_F12: if (otherVal == true) { otherValVal = false; } else { otherVal = true; } break; default: break; } John T You can flip a value like so: myVal = !myVal; so your code would shorten down to: switch(wParam) { case VK_F11: flipVal = !flipVal; break; case VK_F12: otherVal = !otherVal; break; default: break; } Clearly you need a factory pattern!

I was refactoring old code and encountered several IF conditions that were way too complex and long and I'm certain they can be simplified. My guess is that those conditions grew so much because of later modifications. Anyway, I was wondering if any of you know of a good online simplifier I can use. I'm not interested in any specific language, just a simplifier that would take in for example: ((A OR B) AND (!B AND C) OR C) And give me a simplified version of the expression, if any. I've looked at the other similar questions but none point me to a good simplifier. Thanks. 500 - Internal Server

I got screwed when trying to understand this expression. I've thought several times but I cant get the meaning. ! (p || q) is equivalent to !p && !q For this one, somehow I can comprehend a little bit. My understanding is " Not (p q) = not p and not q" which is understandable ! (p && q) is equivalent to !p || !q For the second, I'm totally got screwed. How come My understanding is " Not (p q) = Not p or Not q " . How come and and or can be equivalent each other? as for the rule in the truth table between && and || is different. That's how I comprehend each expression, perhaps I have the wrong

Is there ever a circumstance in which I would not want to use the AndAlso operator rather than the And operator? …or in which I would not want to use the OrElse operator rather than the Or operator? From MSDN : Short-Circuiting Trade-Offs Short-circuiting can improve performance by not evaluating an expression that cannot alter the result of the logical operation. However, if that expression performs additional actions, short-circuiting skips those actions. For example, if the expression includes a call to a Function procedure, that procedure is not called if the expression is short-circuited,

-1 == true; //false -1 == false //false -1 ? true : false; //true Can anyone explain the above output? I know I could work round this by comparing to 0 but I'm interested. I'd expect at least one of the sloppy equals statements to be true as they do implicit type conversion, and I certainly didn't expect the ternary to come up with a totally different result. Andy E In the first two cases, the boolean is cast to a number - 1 for true and 0 for false . In the final case, it is a number that is cast to a boolean and any number except for 0 and NaN will cast to true . So your test cases are