logical-operators | 易学教程

Trouble with Logical and Conditional Operators

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问题 I am having trouble figuring out the proper implementation using logical/conditional operators. I have a very specific requirement for an application and I thought at first it was working correctly, but when placed on the Marketplace I come to find out my implementation is not working at all. If my application is in trial mode and the count of saved occurrences is > 100 the I need to perform an action. If the application is in Trial mode and the count of saved occurrences is <= 100, or the

java logical not operator [duplicate]

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问题 This question already has answers here : What does an exclamation mark mean in Java? (6 answers) Closed last year . This is a silly question but I just want to understand it clearly before I start using it. if (!ServiceHelpers.DISCOVER) { ServiceHelpers.discover(MainActivity.this, peerList); } I would like to know what !ServiceHelpers.DISCOVER mean? 回答1: ! operator inverts the value of a boolean . In this case the boolean is ServiceHelpers.DISCOVER . If it's value is true the ! operator will

Trying to make a random “password generator” in C

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问题 #include <stdio.h> #include <stdlib.h> #include <time.h> int main() int counter = 0; srandom(time(NULL)); // Correct seeding function for random() char randChar; int passwordLength; printf("Give password length \n"); scanf("%d", &passwordLength); while (counter < passwordLength) { randChar = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"[random() % 62]; printf("Your password is: %c", randChar); counter++; } if (passwordLength < 5 && passwordLength>25) { printf("Your password

Q2: AttributeError: 'builtin_function_or_method' object has no attribute 'size'

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问题 Could anyone tell me why I'm getting the error type: AttributeError: 'builtin_function_or_method' object has no attribute 'size' in like 57? for this synthax: out=np.zeros((x.size,y.size)) import numpy as np import sympy as sp from numpy import exp,sqrt,pi from sympy import Integral, log, exp, sqrt, pi import math from numpy import array import matplotlib.pyplot as plt import scipy.integrate from scipy.special import erf from scipy.stats import norm, gaussian_kde from quantecon import LAE

Alternative to which() when no match is found in R

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问题 The which command removes all rows of data if no element was TRUE . Demonstrating with the iris dataset, let's try to remove rows for a non-existing species. dim(iris[-which(iris$Species=="nonsense"),]) # [1] 0 5 All rows are deleted, but using the condition directly returns the expected result. dim(iris[iris$Species!="nonsense",]) # [1] 150 5 This issue was addressed here, and the accepted answer suggested the != solution above. However, I need to store the condition result in a variable. x

PHP eval() logical operator error

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问题 Why does if (isset($_SESSION['location']) AND !empty($_SESSION['location'])) work while if (isset($_SESSION['location']) && !empty($_SESSION['location'])) does not? I'm using eval() to process PHP in a wordpress page. It makes no sense to me why PHP chokes on && and not AND . The docs don't say anything specifically and no one else seems to have a clear answer. Thanks for your input. EDIT Not that it really matters, but I use eval() in a WP template: $sContent = get_the_content(); $sContent =

not boolean value but use ||

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问题 the below code get the window size in different browsers. <!DOCTYPE html> <html> <body> <p id="demo"></p> <script> var w = window.innerWidth || document.documentElement.clientWidth || document.body.clientWidth; var h = window.innerHeight || document.documentElement.clientHeight || document.body.clientHeight; var x = document.getElementById("demo"); x.innerHTML = "Browser inner window width: " + w + ", height: " + h + "."; </script> </body> </html> I want to ask window.innerWidth OR document

Possible to have logical operations (e.g. `ndarray.eq`) not return `bool` in NumPy?

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问题 Question What's the most elegant way to have NumPy not always force np.equal / np.ndarray.__eq__ return arrays of type bool , especially when dtype=object ? Problem Project issue: https://github.com/RobotLocomotion/drake/issues/8315 We're presently using NumPy in a project, and we have symbolic scalars that we're using in the arrays. We define __eq__ to return a formula - here's a simple class that kinda reflects it: import numpy as np class Custom(object): def __init__(self, value): self

Referencing logical operators

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问题 I want to store tuples {a implies c, not c,...} . How do I reference the operators? Is there a specific vocabulary I should use? edited after first comment 来源： https://stackoverflow.com/questions/38776523/referencing-logical-operators

When to use the double logical not (!!) in C? [duplicate]

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问题 This question already has answers here : What is “!!” in C? [duplicate] (7 answers) Closed 5 years ago . What are some valid uses for negating twice in C? For example, something like: if (!!my_cond) { } As I understand, the !! will guarantee that the !!my_cond will be 0 if my_cond is false and 1 otherwise. When would you ever need to use this? 回答1: In the context that you are showing it, it is useless, since the value itself would evaluate to 0 or 1 . It can be usefull in a context that would