boolean-logic

问题 > test = false and true => false > test => false > test = true and false #this is the point I don't understand! => false > test => true Why does ruby behave in this way and how would I use it correctly to not run into this problem? 回答1: Precedence. test = true and false means this: (test = true) and false not this: test = (true and false) Use parentheses as above, or && instead of and , if you want the assignment to come last: test = true && false 来源： https://stackoverflow.com/questions

问题 I am little confused with logical AND operator. I have these 2 lines of code. Here num and j are both int. I have a situation where both the conditions are satisfied, but I don't know why it's not printing the value of j . Can anybody point out the mistakes? Thanks in advance. if(k==1 && num%j==0) printf("%d",j); 回答1: In plain English, the expression k == 1 && num % j == 0 is true if and only if k equals 1 and the remainder from dividing num by j is 0. Not much more I can say. 回答2: There's

问题 I want to validate a string in javascript that contains a Boolean expression with brackets. The string should only contain numbers 1-9 , () , OR , AND . Examples of good strings: "1 AND 2" "2 OR 4" "4 AND (3 OR 5)" I am not sure if Regular Expression are flexible enough for this task. Is there a nice short way of achieving this in javascript ? 回答1: In JavaScript, you can use the following. replace 'AND/OR/NOT' with '&&/||/!'. use eval to evaluate it. Careful because eval is a powerful

问题 I'm trying to get this to evaluate to false. (False,) It's currently equaled to true, because I think the tuple is not empty. So how might one extract or cast this to a boolean? Thanks~ 回答1: Extract the element from the tuple is the most simple approach: value = (False,)[0] Python2 is more lenient, but in general it isn't good practice to treat a tuple as a single value for comparison purposes (Python3 explicetly bans it) Instead, look at the all and any functions for this behavior. As always

问题 I have the following function to be reduced/simplified. F(A,B,C,D) = BC + (A + C'D') where ' denotes the complement Here's my solution: = BC + (A + C'D')' = BC + (A + (C+D) = BC + (A + C + D) = BC + C + A + D = C(B + 1) + A + D = C*1 + A + D = C + A + D Is this correct? 回答1: As in traditional algebra, if you do something to one side of the equation, you must do it to the other side, including complementing. Here we state the original equation: F'(A,B,C,D) = BC + (A + (CD)') Since we have F'

问题 The other day I was trying to code a small C++ programming using the SDL multimedia library, and I ran into this small snag which I eventually solved through trial and error. The issue is, I understand what I did to solve the problem, but I don't really understand the nature of the problem! The issue was with keyboard event handling in SDL. The code to handle a single key press to exit the program is straight forward and simple. [eventQueue is an SDL_Event structure] //checks for keypress

问题 I'm writing cycle based logic simulation in C#. I want to simulate both combinational and sequential circuits. Combinational circuits are straightforward but sequential circuits give me trouble. I want to detect oscillations and display appropriate warning message. Is there a simple way to check how many times a single gate can change its state and still leave the circuit stable? I thought about 'minimum feedback arc set algorithm' but it seems to be an overkill. Many desktop applications

问题 I want to grab all documents with loId=6 AND (actionType = "SAVE_DATA" OR actionType = "OPEN_SCREEN") . Am I writing this logic incorrectly? Why does my query return 0 results? Note : I'd accept a query or a filter to resolve this issue. These are some sample documents: { "_index": "logs", "_type": "record", "_id": "eIIt3vtrSxmdOVGClQmN3w", "_score": 1, "_source": { "timestamp": 1373569919000, "uid": 6, "paId": 56298, "loId": 6, "prId": 2, "vId": 6577, "actionType": "SAVE_DATA" } }, { "_index

问题 This runs in ActionScript 3 and JavaScript. Why? I know how && and || work, but a list? Is this AS3 specific? Is this in other languages? I'm a mouth breathing PHP/AS2 programmer. Or did everyone already know this and I'm a tool for not reading documentation properly? AS3 if (true, true, true) { trace("true?") } //result - "true?" traced JavaScript if (true, true, true) { alert("true?"); } //result - "true?" alert message popped up if (false, false, false) { alert("true?"); } else { alert(

问题 Im reading Jon Skeet book. (#4) but one thing (among others) caught my eye : topic : bool? he wrote in a table that :(X,Y are bool?) X | Y | X & Y --------------------------- true null null ok fine... so the null is the one who decides. the bool operand here looses. X | Y | X & Y --------------------------- false null false why ? why the bool operand here is being taking into account while in the previous sample it was the null who decided about the result ...? It seems that true and false