global-variables

问题 This question already has an answer here : extern auto variable has no initializer (1 answer) Closed 4 months ago . Somewhat similar to this post, but still different: can I define a global auto variable in some header file? I tried using the following files, but couldn't make them compile. $ cat main.cpp auto a = 5; #include "defs.h" int main(int argc, char **argv){ return a; } $ cat defs.h #ifndef __DEFS_H__ #define __DEFS_H__ extern auto a; #endif And after standard compilation ( g++ main

问题 What is the difference between declaring a variable within a function as global or public/private VS passing it to a function as an argument? Other related confusion I've recently caused myself a big headache trying to pass aa array variable into a function as global and editing it inside and hoping to return it altered, and it took me hours to figure out that I needed to pass it into the function as an argument by reference, like functionCall(&$arrayVar); Secondary question: But I am still

问题 In JavaScript, is it possible to specify the global context which will be used if a local variable isn't defined? Example: (function foo() { console.log(bar); })(); It will actually print window.bar . Can I somehow change the global context? Something like this: var myGlobalContext = { bar: "foo" }; (function foo() { console.log(bar); }).applyWithGlobal(myGlobalContext); It should print myGlobalContext.bar . Or attach this to be the global context? I hope the example is clear enough. 回答1: The

问题 I investigated that scope of global variables in python is limited to the module. But I need the scope to be global among different modules. Is there such a thing? I played around __builtin__ but no luck. thanks in advance! 回答1: You can access global variables from other modules by importing them explicitly. In module foo : joe = 5 In module bar : from foo import joe print joe Note that this isn't recommended, though. It's much better to hide access to a module's variables by using functions.

问题 I'm working on a project where there are some global assignments, and I ran into something sort of odd. I was hoping someone could help me with it. I wrote this toy example to demonstrate the problem: x <- 1:3 ; x <- c(1, 2, 5) # this works fine x <- 1:3 ; x[3] <- 5 # this works fine x <<- 1:3 ; x <<- c(1, 2, 5) # this works fine x <<- 1:3 ; x[3] <<- 5 # this does not work # Error in x[3] <<- 5 : object 'x' not found same.thing.but.in.a.function = function() { x <<- 1:3 x[3] <<- 5 } same

问题 I'm working with two js files and sharing variables between them in a titanium app. In my main app.js I have 3 variables associated with each row in a table. I have an event listener for when a row is clicked to open a modal view whose components are in a separate js file. My three variables are below and on the click event I have an alert of the 3 variables and the 3 global variables. var titleText = titleInRow.text; var artistText=artistInRow.text; Ti.App.myGlobalSongVar = titleText; Ti.App

问题 A couple years ago I learned that global variables are bad and should be avoided. But I know they are sometimes unavoidable, at least in an embedded system. What do you think is the most elegant way to work with them? In my projects I have a file called globals.h where I define all my global variables: #ifndef GLOBALS_H #define GLOBALS_H extern int16_t gVariable1; extern int16_t gVariable2; …. #endif In my main project file I declare all global variables: /* **********************************

问题 Simply, how do I create a global variable in JSP, such that I can access it across other JSP pages and/or inside frames/iframes? I tried <%!..%> but I got an error that the variable could not be resolved in a separate jsp page. Is it even possible to access JSP variables in more than one page without resorting to query strings, session variables, etcetera? Thank you. 回答1: As I've already commented, you can use ServletContext to maintain the variables for all your application. Do not confuse

问题 I read that gcc provides support to define global variables as register stored variables. What I want to know is that do the standards have any specifications for this support. 回答1: There is a common misconsception that C's keyword register talks about hardware registers. That might be the origin of that concept, but in modern C this is not the purpose. The only real effect that register has, is that the & is not allowed on such a beast. They may be realized in any way the compiler wants,

问题 Following up on Reason for unintuitive UnboundLocalError behaviour (I will assume you've read it). Consider the following Python script: def f(): # a+=1 # 1 aa=a aa+=1 # b+='b' # 2 bb=b bb+='b' c[0]+='c' # 3 c.append('c') cc=c cc.append('c') d['d']=5 # Update 1 d['dd']=6 # Update 1 dd=d # Update 1 dd['ddd']=7 # Update 1 e.add('e') # Update 2 ee=e # Update 2 ee.add('e') # Update 2 a=1 b='b' c=['c'] d={'d':4} # Update 1 e=set(['e']) # Update 2 f() print a print b print c print d # Update 1