boolean-expression | 易学教程

Any good boolean expression simplifiers out there? [closed]

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问题 Closed. This question is off-topic. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 4 years ago . 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

How to understand De Morgan Laws Boolean Expression

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问题 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

Why does Perl use the empty string to represent the boolean false value?

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问题 When evaluating an expression in a scalar (boolean) context, Perl uses the explicit value 1 as a result if the expression evaluates to true and the empty string if the expression evaluates to false. I'm curious why Perl uses the empty string to represent boolean false value and not 0 which seems more intuitive. Note that I'm not concerned with Perl treating the empty string as a false in scalar (boolean) context. EDIT How would using string which is true ( "false" for instance) as a string

boolean expression parser in java

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Are there any java libraries or techniques to parsing boolean expressions piecemeal? What I mean is given an expression like this: T && ( F || ( F && T ) ) It could be broken down into a expression tree to show which token caused the 'F' value, like so ( maybe something like this): T && <- rhs false ( F || <- rhs false ( F && T ) <- eval, false ) I am trying to communicate boolean expression evaluations to non-programmers. I have poked around with Anlr, but I couldn't get it to do much (it seems to have a bit of a learning curve). I'm not opposed to writing it myself, but I'd rather not

Python `if x is not None` or `if not x is None`?

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I've always thought of the if not x is None version to be more clear, but Google's style guide and PEP-8 both use if x is not None . Is there any minor performance difference (I'm assuming not), and is there any case where one really doesn't fit (making the other a clear winner for my convention)?* *I'm referring to any singleton, rather than just None . ...to compare singletons like None. Use is or is not. There's no performance difference, as they compile to the same bytecode: Python 2.6.2 (r262:71600, Apr 15 2009, 07:20:39) >>> import dis >>> def f(x): ... return x is not None ... >>> dis

“Boolean” operations in Python (ie: the and/or operators)

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问题 This method searches for the first group of word characters (ie: [a-zA-Z0-9_] ), returning the first matched group or None in case of failure. def test(str): m = re.search(r\'(\\w+)\', str) if m: return m.group(1) return None The same function can be rewritten as: def test2(str): m = re.search(r\'(\\w+)\', str) return m and m.group(1) This works the same, and is documented behavior; as this page clearly states: The expression x and y first evaluates x ; if x is false, its value is returned;

boolean expression parser in java

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问题 Are there any java libraries or techniques to parsing boolean expressions piecemeal? What I mean is given an expression like this: T && ( F || ( F && T ) ) It could be broken down into a expression tree to show which token caused the \'F\' value, like so ( maybe something like this): T && <- rhs false ( F || <- rhs false ( F && T ) <- eval, false ) I am trying to communicate boolean expression evaluations to non-programmers. I have poked around with Anlr, but I couldn\'t get it to do much (it

Python `if x is not None` or `if not x is None`?

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问题 I\'ve always thought of the if not x is None version to be more clear, but Google\'s style guide and PEP-8 both use if x is not None . Is there any minor performance difference (I\'m assuming not), and is there any case where one really doesn\'t fit (making the other a clear winner for my convention)?* *I\'m referring to any singleton, rather than just None . ...to compare singletons like None. Use is or is not. 回答1: There's no performance difference, as they compile to the same bytecode:

Priority of the logical statements NOT AND & OR in python

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问题 As far as I know, in C & C++, the priority sequence for NOT AND & OR is NOT>AND>OR. But this doesn\'t seem to work in a similar way in Python. I tried searching for it in the Python documentation and failed (Guess I\'m a little impatient.). Can someone clear this up for me? 回答1: It's NOT, AND, OR, from highest to lowest according to the documentation https://docs.python.org/3/reference/expressions.html#operator-precedence Here is the complete precedence table, lowest precedence to highest. A

Merge lists that share common elements

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问题 My input is a list of lists. Some of them share common elements, eg. L = [[\'a\',\'b\',\'c\'],[\'b\',\'d\',\'e\'],[\'k\'],[\'o\',\'p\'],[\'e\',\'f\'],[\'p\',\'a\'],[\'d\',\'g\']] I need to merge all lists, that share a common element, and repeat this procedure as long as there are no more lists with the same item. I thought about using boolean operations and a while loop, but couldn\'t come up with a good solution. The final result should be: L = [[\'a\',\'b\',\'c\',\'d\',\'e\',\'f\',\'g\',\