boolean-expression | 易学教程

Any good boolean expression simplifiers out there? [closed]

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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

How to understand De Morgan Laws Boolean Expression

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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

Boolean logic in RESTful filtering and queries

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问题 This is sort of a follow-up to someone else's question about filtering/querying a list of cars. There the recommendation for a RESTful filtering request was to put filter expressions in the query of the URI, like this: /cars?color=blue&type=sedan&doors=4 That's fine. But what if my filtering query becomes more complicated and I need to use Boolean operators, such as: ((color=blue OR type=sedan) AND doors=4) OR color=red That is, I want to find a four-door blue car or a four-door sedan, but if

XOR of three values

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What is the simplest way to do a three-way exclusive OR? In other words, I have three values, and I want a statement that evaluates to true IFF only one of the three values is true. So far, this is what I've come up with: ((a ^ b) && (a ^ c) && !(b && c)) || ((b ^ a) && (b ^ c) && !(a && c)) || ((c ^ a) && (c ^ b) && !(a && b)) Is there something simpler to do the same thing? Here's the proof that the above accomplishes the task: a = true; b = true; c = true ((a ^ b) && (a ^ c) && !(b && c)) || ((b ^ a) && (b ^ c) && !(a && c)) || ((c ^ a) && (c ^ b) && !(a && b)) => false a = true; b = true;

Is there a difference between “== False” and “is not” when checking for an empty string?

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问题 I have read elsewhere on stackoverflow that the most elegant way to check for an empty string in Python (e.g. let's say it's a string called response ) is to do: if not response: # do some stuff The reason being that strings can evaluate to boolean objects. So my question is, does the below code say the same thing? if response == False: # do some stuff 回答1: As already mentioned there is a difference. The not response checks if bool(response) == False or failing that if len(response) == 0 so

What does the exclamation mark mean in an Objective-C if statement?

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问题 I am wondering what the exclamation mark in if(!anObject) means. 回答1: It is the boolean NOT operator also called negation. !true == false; !false == true; 回答2: That is the Logical NOT operator, i.e., if( thisThisIsNotTrue ) { doStuff } . 回答3: It's a C operator, simply meaning "not". So !YES == NO and !NO == YES are both true statements. if (![txtOperator.text isEqualToString: @"+"]) , for example, checks to see if txtOperator.text is NOT equal to @"+". 回答4: If it always adds, then your string

Cleanest way to convert to boolean [duplicate]

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问题 This question already has an answer here: How can I convert a string to boolean in JavaScript? 75 answers I have a variable. Let's call it toto . This toto can be set to undefined , null , a string, or an object. I would like the cleanest way to check if toto is set to a data, which means set to a string or an object, and neither undefined nor null , and set corresponding boolean value in another variable. I thought to the syntax !! , that would look like this: var tata = !!toto; // tata

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

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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; otherwise, y is evaluated and the resulting value is returned. However, being a boolean operator (it even says

Python boolean expression and or

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问题 In python if you write something like foo==bar and spam or eggs python appears to return spam if the boolean statement is true and eggs otherwise. Could someone explain this behaviour? Why is the expression not being evaluated like one long boolean? Edit: Specifically, I'm trying to figure out the mechanism why 'spam' or 'eggs' is being returned as the result of the expression. 回答1: The operators and and or are short-circuiting which means that if the result of the expression can be deduced

Boolean expression order of evaluation in Java?

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问题 Suppose I have the following expression String myString = getStringFromSomeExternalSource(); if (myString != null && myString.trim().length() != 0) { ... } Eclipse warns me that myString might be null in the second phrase of the boolean expression. However, I know some that some compilers will exit the boolean expression entirely if the first condition fails. Is this true with Java? Or is the order of evaluation not guaranteed? 回答1: However, I know some that some compilers will exit the