logical-operators | 易学教程

Apache - Limitations of logically linking RewriteCond in 2.2/2.4

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问题 These days I read a very interesting post about the precedence of [OR] over the implicit [AND] . I really liked the original question as well as highly appreciated answer. I just recently stumbled upon further problems concerning this topic. The problems start as soon as you try to express the following: RewriteCond A RewriteCond B RewriteCond C RewriteRule ... with A OR (B AND C) . Where ever you place the [OR] , it won't work: #resolves to (A OR B) AND C RewriteCond A [OR] RewriteCond B

do | and & make any sense in java?

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问题 Rarely I bump into & and | logic operators in other's codes instead of || and &&. I made a quick research because I never used them and didn't know what is it for. A && B means if A is false, B won't be evaluated and it will return false. A & B means if A is false, B will be evaluated even if the form will return false as well. Of course it is the same game with | and ||. My question is: does it make sense anyways to evaluate the second member if the first determine the evaluation? I can

How does the compiler evaluate a condition in C

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问题 I have a question regarding how the compiler evaluates 'AND' condition in c. Say, I write a statement like if( (today is Thursday) && (Month is July) ) { //do something } Assume today is not Thursday, but the Month is indeed July. Does the compiler check both the conditions, and do 1&0 == 0? Or as soon as it sees that today is not Thursday, it just skips out and doesn't even bother to check the Month condition since it's inconsequential. I'm using the following gcc Using built-in specs.

In Ruby, should we always use “&&”, “||” instead of “and”, “or” unless for special situations? [closed]

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问题 It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, visit the help center. Closed 9 years ago . Is it true that in most cases, in Ruby, it is best to use && , || instead of and , or , unless it is some special situations. I think one of Ruby's design principles is to have least surprises as possible, so

Precedence of Logical Operators in C [duplicate]

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问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: why “++x || ++y && ++z” calculate “++x” firstly ? however,Operator “&&” is higher than “||” If you look at C's precedence table, you'll see that && has higher precedence than ||. But take a look at the following code: a=b=c=1; ++a || ++b && ++c; printf("%d %d %d\n",a,b,c); It prints out "2 1 1", meaning that the "++a" is evaluated first, and once the program sees a TRUE there it stops right there, because what

Why is {} < function(){}?

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问题 While I was messing around with truth tables in JavaScript, I noticed that the following evaluates to true: var a, b, c; a = {}; b = function(){}; c = a < b; console.log(c); Why? I've only tested this in Firefox, and I'm sure I could dig up the details in the ECMAScript 2.6.2 spec, but TBH I'm feeling lazy. 回答1: JavaScript type coercion makes the comparison essentially String({}) < String(function(){}) so essentially you are just doing "[object Object]" < "function (){}" which is a

If Statement not working with And (&&) Operator

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I'm having a hard time writing up what seems should be a simple if statement! I need it to say if mod does not equal a, b, or c - then do this. Here is what I was trying but have been unsuccessful: var mod = CURRENT_MODULE_ID; if (mod != "5827289" && mod != "5195103" && mod != "5181422") { doSomething(); } When I type this into my editor it says there is an error, specifically that "The entity name must immediately follow the '&' in the entity reference." .. and is not working when I go to test. Any help is appreciated!! UPDATE: The url: esber.squarespace.com The full script: <script type=

Is it possible to overload logical and in Python?

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I was under the impression it was possible to overload and in Python, but reading through the docs just now, I realized that __and__ refers to the bitwise & operator, not logical and . Am I overlooking something, or is it not possible to overload logical and in Python? No this is not possible. There is a proposal that adds this functionality but for now, it is rejected. rkrzr No, it is not possible. See here . There is no straight way to do this. You could override __nonzero__ for your objects to modify their truth value. class Truth: def __init__(self, truth): self.truth = truth def __nonzero

excel using cell reference as a logical operator and looking up a value

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I have a table to lookup a value like this: logical test | points -------------|------- <= 0 | 1 <= 10 | 2 <= 20 | 4 > 20 | 5 If my cell is (A1 for example) <= 0 the result is 1... if my cell is <=10 the result is 2 ... if my cell is > 20 the result is 5. I could use several if functions for that, but I want to prevent the user to have to change the formula if the table changes. For example, if, for some reason, the first line changes to > 0 it wouldn't be necessary to change the formula. I have tried using concatenate(mycell;logical_operator;logical_value) inside the if function but it doesn

do | and & make any sense in java?

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Rarely I bump into & and | logic operators in other's codes instead of || and &&. I made a quick research because I never used them and didn't know what is it for. A && B means if A is false, B won't be evaluated and it will return false. A & B means if A is false, B will be evaluated even if the form will return false as well. Of course it is the same game with | and ||. My question is: does it make sense anyways to evaluate the second member if the first determine the evaluation? I can imagine a code where the second member does something super important logic in clode and so it should be