I find it easiest to understand move semantics with example code. Let’s start with a very simple string class which only holds a pointer to a heap-allocated block of memory: #include <cstring> #include <algorithm> class string { char* data; public: string(const char* p) { size_t size = std::strlen(p) + 1; data = new char[size]; std::memcpy(data, … Read more
extern “C” makes a function-name in C++ have C linkage (compiler does not mangle the name) so that client C code can link to (use) your function using a C compatible header file that contains just the declaration of your function. Your function definition is contained in a binary format (that was compiled by your … Read more
If your goal is to use a profiler, use one of the suggested ones. However, if you’re in a hurry and you can manually interrupt your program under the debugger while it’s being subjectively slow, there’s a simple way to find performance problems. Just halt it several times, and each time look at the call … Read more
UPDATE This answer is rather old, and so describes what was ‘good’ at the time, which was smart pointers provided by the Boost library. Since C++11, the standard library has provided sufficient smart pointers types, and so you should favour the use of std::unique_ptr, std::shared_ptr and std::weak_ptr. There was also std::auto_ptr. It was very much … Read more
You can use a library called ExcelLibrary. It’s a free, open source library posted on Google Code: ExcelLibrary This looks to be a port of the PHP ExcelWriter that you mentioned above. It will not write to the new .xlsx format yet, but they are working on adding that functionality in. It’s very simple, small … Read more
tl;dr: Because of different default settings in C++ requiring more system calls. By default, cin is synchronized with stdio, which causes it to avoid any input buffering. If you add this to the top of your main, you should see much better performance: std::ios_base::sync_with_stdio(false); Normally, when an input stream is buffered, instead of reading one … Read more
Caveat: It is not necessary to put the implementation in the header file, see the alternative solution at the end of this answer. Anyway, the reason your code is failing is that, when instantiating a template, the compiler creates a new class with the given template argument. For example: template<typename T> struct Foo { T … Read more
First, you have to learn to think like a Language Lawyer. The C++ specification does not make reference to any particular compiler, operating system, or CPU. It makes reference to an abstract machine that is a generalization of actual systems. In the Language Lawyer world, the job of the programmer is to write code for … Read more
An easy to understand and simple solution. // Save today’s date. var today = DateTime.Today; // Calculate the age. var age = today.Year – birthdate.Year; // Go back to the year in which the person was born in case of a leap year if (birthdate.Date > today.AddYears(-age)) age–; However, this assumes you are looking for … Read more
Just cast the enum, e.g. int something = (int) Question.Role; The above will work for the vast majority of enums you see in the wild, as the default underlying type for an enum is int. However, as cecilphillip points out, enums can have different underlying types. If an enum is declared as a uint, long, … Read more