logical-operators

问题 One of the things I like the most of JavaScript is that the logical operators are very powerful: && can be used to safely extract the value of an object's field, and will return null if either the object or the field has not been initialized // returns null if param, param.object or param.object.field // have not been set field = param && param.object && param.object.field; || can be used to set default values: // set param to its default value param = param || defaultValue; Does PHP allow

问题 One of the things I like the most of JavaScript is that the logical operators are very powerful: && can be used to safely extract the value of an object's field, and will return null if either the object or the field has not been initialized // returns null if param, param.object or param.object.field // have not been set field = param && param.object && param.object.field; || can be used to set default values: // set param to its default value param = param || defaultValue; Does PHP allow

问题 I'm trying to use only AND OR XOR and NOT to determine whether adding 2 binary number made of 4 bits will overflow. I know, for example, that something like 1100 + 0100 will wind up as 1 | 0000. But how can I find this using just these logical operators? I'm trying to get 1000 when overflow happens, and 0000 when it doesn't. This is easy enough since I can just use XOR with a mask to clear the last 3 bits. Does anyone have suggestions for figuring this out? 回答1: Numbers are ABCD and EFGH, ^

问题 I am newbie to MongoDB and need to query MongoDB in Java. For simple queries, I can write the equivalent Java code but the below query is a little complex and not getting how to write equivalent Java code. Below is the equivalent MongoDB query db.FILE_JOURNEY.find( {$and :[ { $or: [ { SUBSCRIBERID: "225136298" }, { SUBSCRIBERID : null} ] }, { $or: [ { BATCHID : "615060299" }, { FILENAME : "TR.NYHBE.834Q.D.212311980342.QHP.dat" } ] } ] } ) Here, FILE_JOURNEY is the collection. 回答1: It can be

问题 Is it possible in Handlebars to check if a string is equal to another value without registering a helper? I can't seem to find anything relevant to this in the Handlebars reference. For example: {{#if sampleString == "This is a string"}} ...do something {{/if}} 回答1: It seems you can't do it "directly" Try use helper, why not? Register helper in your javascript code: Handlebars.registerHelper('ifEquals', function(arg1, arg2, options) { return (arg1 == arg2) ? options.fn(this) : options.inverse

问题 I don’t understand the difference between & and and , even if I read some other questions about it. My code is: f=1 x=1 f==1 & x==1 Out[60]: True f==1 and x==1 Out[61]: True f=1 x=2 f==1 and x==2 Out[64]: True f==1 & x==2 Out[65]: False Why is it the second & False , whereas the first is True ? 回答1: The issue is that & has higher operator precedence than == . >>> (f == 1) & (x == 2) True >>> f == (1 & x) == 2 False Perhaps this seems unintuitive, but & is really meant to be used between

问题 This question already has answers here : Can you use 2 or more OR conditions in an if statement? (6 answers) Closed 2 years ago . if(1 == 2 || 4) { cout<<"True"; } else { cout<<"False"; } This is how I read the above. If 1 is equal to 2 or 4, then print true. Otherwise, print false. When this is executed though... true is printed. Obviously I'm misunderstanding something here. 1 is not equal to 2 or 4. Wouldn't that make it false? 回答1: Yeah, I've made the same mistake. Read the sentence again

问题 I read the following Stack Overflow questions, and I understand the differences between bitwise and logical. Difference between & and && in PHP Reference - What does this symbol mean in PHP? However, none of them explains when I should use bitwise or logical. When should I use bitwise operators rather than logical ones and vice versa? In which situation do I need to compare bit by bit? I am not asking about the differences, but I am asking the situation when you need to use bitwise operators.

问题 I'm doing an exercise of a book called programming in C language, trying to solve exercise 7.9 and so my code works perfectly until I add a conditional statement for the function to only accept variables greater than 0 I have tried changing it in many ways but nothing seems to work // Program to find the least common multiple #include <stdio.h> int main(void) { int lcm(int u, int v); printf("the least common multiple of 15 and 30 is: %i\n", lcm(15, 30)); return 0; } // Least common multiple

问题 i created a search engine on my site using full text search in Postegresql. i added a searchbox in my PHP page in which users can write strings like these: word1 +word2 word1+word2 word1 -word2 word1-word2 word1 word2 word1 word2 how to convert them to the following strings? word1&word2 word1&word2 word1&!word2 word1&!word2 word1|word2 word1|word2 i tried several solutions but none works with all cases. The last one i tried is the following: $user_query_string = trim($_GET['search']); $final