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c++11 std::call_once只调用一次函数，类似单例模式 - C/C++ - 清泛网 - 专...
...次，Demo如下： include <iostream> include <thread>static std::once_flag g_once_flag std::call_once 保证函数或者一些代码段在并发或者多线程的情况下，始终只会被执行一次，Demo如下：
#include <iostream>
#include <thread>
#include <mutex>
static std::onc...
How to run Conda?
...nda and can run Python, so I assume that I installed it correctly. Following this introductory documentation , I am trying to install Python v3.3, so I am copying and pasting the following line into my console:
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Git: Show all of the various changes to a single line in a specified file over the entire git histor
I've looked around, and am not sure if this is possible, but here goes:
5 Answers
5
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How can I reset or revert a file to a specific revision?
I have made some changes to a file which has been committed a few times as part of a group of files, but now want to reset/revert the changes on it back to a previous version.
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C# Test if user has write access to a folder
I need to test if a user can write to a folder before actually attempting to do so.
18 Answers
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How to detect the OS from a Bash script?
I would like to keep my .bashrc and .bash_login files in version control so that I can use them between all the computers I use. The problem is I have some OS specific aliases so I was looking for a way to determine if the script is running on Mac OS X, Linux or Cygwin .
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What's the bad magic number error?
What's the "Bad magic number" ImportError in python, and how do I fix it?
15 Answers
1...
Why doesn't Java allow generic subclasses of Throwable?
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As mark said, the types are not reifiable, which is a problem in the following case:
try {
doSomeStuff();
} catch (SomeException<Integer> e) {
// ignore that
} catch (SomeException<String> e) {
crashAndBurn()
}
Both SomeException<Intege...
How do I return the response from an asynchronous call?
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→ For a more general explanation of async behaviour with different examples, please see Why is my variable unaltered after I modify it inside of a function? - Asynchronous code reference
→ If you already understand the problem, skip to the possible solutions below....
Is a GUID unique 100% of the time?
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While each generated GUID is not
guaranteed to be unique, the total
number of unique keys (2128 or
3.4×1038) is so large that the probability of the same number being
generated twice is very small. For
example, consider the observable
universe, which contains about 5×10...