global

问题 I am given to believe that random number generators (RNGs) should only be seeded once to ensure that the distribution of results is as intended. I am writing a Monte Carlo simulation in C++ which consists of a main function ("A") calling another function ("B") several times, where a large quantity of random numbers is generated in B. Currently, I am doing the following in B: void B(){ std::array<int, std::mt19937::state_size> seed_data; std::random_device r; std::generate(seed_data.begin(),

问题 Is there a way to prevent a function from using global variables like document , window , navigator , and other declared global functions ? EDIT1: And if I could choose which global objects that are restricted it would be great, because I would like to allow the function to use for an example the Math object and it's functions... 回答1: Is there a way to prevent a function from using global variables like document, window, navigator, and other declared global functions? No, unless... The only

问题 Here im having a bit of an issue with this very simple script Ive written up. The aim for this script is to simply reduce the given number by one each time the button is clicked. I cannot appear to do this.. My global variable being the Number=100 doesnt appear to change, or change more than once.. Apologies for not being able to explain this well. Here is the part im working on..: <script> var Number = 100; // Number i want changed and to keep changing each button click function outcome() {

问题 I am currently trying to program an online drawing program using the HTML5 canvas. The thing is, I need to have the current canvas saved somewhere globally. Static variables work, but they do not get shared across a Webgarden. This results in two different drawings being created. I will have to somehow create a new application object which is shared. I figured I will need an external application holding them. 1) How do I replace the application object with my own? So either I will have to

问题 So I have a class in a module that has some static methods. A couple of these static methods just do crc checks and stuff, and they're not really useful outside of the class (I would just make them private static methods in java or C++). I'm wondering if I should instead make them global class functions (outside of the class). Is there any benefit for doing it either way? The class is being imported by from module import class so I'm not worried about having those modules pulled in as well.

问题 How can I use global DB variable inside class? Let's say I have this in my config.php $dbh = new PDO("mysql:host=localhost;dbname=mydb", "root", ""); and I want to use this $dbh inside class as follows (MyClass.php) class MyClass { public function DoSomething($plogin_id) { $sql = "SELECT * FROM mytable WHERE login_id = :login_id"; $stmt = $dbh->prepare($sql); //line 14 $stmt->bindParam(':login_id', $plogin_id, PDO::PARAM_STR); } } And inside my index.php file I am using this MyClass as

问题 For many of my java projects, I use database extensively, what I usually do is to have a property.xml file to hold all my strings and settings. And then I would have a class CNST to hold all the static constants corresponding to those in the xml file. Those constants are initialized by the xml file once when the program starts, and used as globals anywhere later on in the program. However, after reading many articles these days, it seems that using globals at all is not such a good practice.

问题 I am trying to add my own error handling to the JavaScript setTimeout function. The following code works fine in chrome: var oldSetTimeout = window.setTimeout; window.setTimeout = function setTimeout(func, delay) { var args = Array.prototype.slice.call(arguments, 0); args[0] = function timeoutFunction() { var timeoutArgs = Array.prototype.slice.call(arguments, 0); try { func.apply(this,timeoutArgs); } catch (exception) { //Do Error Handling } } return oldSetTimeout.apply(this, args); } But in

问题 I have around 40 models in my RoR application. I want to setup a after_save callback for all models. One way is to add it to all models. Since this callback has the same code to run, is there a way to define it globally once so that it gets invoked for all models. I tried this with no luck: class ActiveRecord::Base after_save :do_something def do_something # .... end end Same code works if I do it in individual models. Thanks, Imran 回答1: You should use observers for this: class AuditObserver

问题 I want to define a list that a user may update through doing certain actions. I did this: runApp(list( ui=fluidPage( h1('Example') ,textInput('txt','','Text') ,actionButton('add','add') ,verbatimTextOutput('list') )#ui ,server=function(input,output,session) { s.list<-reactive(isolate(d.list())) d.list<-reactive({if (input$add == 0) return() isolate({ list(input$txt,unlist(s.list())) })#iso })#rea output$list<-renderPrint({ list(unlist(d.list())) })#list }#server ))#ruanApp But the list