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QString to char* conversion
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Specifically C++ temporaries normally live until the end of the statement that creates them. So the first form in the answer is ok if it's used in-line in a function call (assuming the function doesn't store the pointer for future use) bu...
What happens when a computer program runs?
... It is commonly used for data structures that you allocate at runtime (in C++, using new and delete, and malloc and friends in C, etc).
The stack and heap, on the x86 architecture, both physically reside in your system memory (RAM), and are mapped through virtual memory allocation into the process...
Using a dictionary to count the items in a list [duplicate]
...ation of a multiset which is not an uncommon data structure IMO. In fact, C++ has an implementation in the STL called std::multiset (also std::tr1::unordered_multiset) so Guido is not alone in his opinion of its importance.
– awesomo
Oct 18 '11 at 3:07
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Initializing a two dimensional std::vector
...BER, 4));
I should also mention uniform initialization was introduced in C++11, which permits the initialization of vector, and other containers, using {}:
std::vector<std::vector<int> > fog { { 1, 1, 1 },
{ 2, 2, 2 } };
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Get current date in milliseconds
...language you desire. Here is the list -
ActionScript (new Date()).time
C++ std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::system_clock::now().time_since_epoch()).count()
C#.NET DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()
Clojure (System/currentTimeMillis)
Excel / Go...
Java Annotations
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Also, are they unique to Java, is there a C++ equivalent?
No, but VB and C# have attributes which are the same thing.
Their use is quite diverse. One typical Java example, @Override has no effect on the code but it can be used by the compiler to generate a warning...
How to define a preprocessor symbol in Xcode
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For Xcode 9.4.1 and C++ project. Adding const char* Preprocessor Macros to both Debug and Release builds.
Select your project
Select Build Settings
Search "Preprocessor Macros"
Open interactive list
Add your macros and don't forget to...
Is there any performance reason to declare method parameters final in Java?
...e type, such as int, and inline them directly in the code just like with a C++ macro.
However, i have no clue if this is done in practice, but it could be done in order to save some memory.
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How to check if a file is empty in Bash?
... the shell cannot help you when you misspell, whereas a compiler like your C++ compiler can help you.
Notice incidentally that I have swapped the roles of empty.txt and full.txt, as @Matthias suggests.
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How to map atan2() to degrees 0-360
...(theta_rad/M_PI*180) + (theta_rad > 0 ? 0 : 360);
This should work in C++: (depending on how fmod is implemented, it may be faster or slower than the conditional expression)
theta_deg = fmod(atan2(y,x)/M_PI*180,360);
Alternatively you could do this:
theta_deg = atan2(-y,-x)/M_PI*180 + 180;
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