I’ve been looking into some of the new features of C++11 and one I’ve noticed is the double ampersand in declaring variables, like T&& var. For a start, what is this beast called? I wish Google would allow us to search for punctuation like this. What exactly does it mean? At first glance, it appears … Read more
I keep hearing a lot about functors in C++. Can someone give me an overview as to what they are and in what cases they would be useful? 14 s 14 A functor is pretty much just a class which defines the operator(). That lets you create objects which “look like” a function: // this … Read more
I’m a bit confused regarding the difference between push_back and emplace_back. void emplace_back(Type&& _Val); void push_back(const Type& _Val); void push_back(Type&& _Val); As there is a push_back overload taking a rvalue reference I don’t quite see what the purpose of emplace_back becomes? 7 s 7 In addition to what visitor said : The function void emplace_back(Type&& … Read more
It’s common in C++ to name member variables with some kind of prefix to denote the fact that they’re member variables, rather than local variables or parameters. If you’ve come from an MFC background, you’ll probably use m_foo. I’ve also seen myFoo occasionally. C# (or possibly just .NET) seems to recommend using just an underscore, … Read more
This question’s answers are a community effort. Edit existing answers to improve this post. It is not currently accepting new answers or interactions. C++17 is now feature complete, so unlikely to experience large changes. Hundreds of proposals were put forward for C++17. Which of those features were added to C++ in C++17? When using a … Read more
How can I convert an std::string to a char* or a const char*? 10 s 10 If you just want to pass a std::string to a function that needs const char* you can use std::string str; const char * c = str.c_str(); If you want to get a writable copy, like char *, you can … Read more
What are “sequence points”? What is the relation between undefined behaviour and sequence points? I often use funny and convoluted expressions like a[++i] = i;, to make myself feel better. Why should I stop using them? If you’ve read this, be sure to visit the follow-up question Undefined behavior and sequence points reloaded. (Note: This … Read more
What is the difference between g++ and gcc? Which one of them should be used for general c++ development? 10 s 10
I’ve always wondered this – why can’t you declare variables after a case label in a switch statement? In C++ you can declare variables pretty much anywhere (and declaring them close to first use is obviously a good thing) but the following still won’t work: switch (val) { case VAL: // This won’t work int … Read more
As a C# developer I’m used to running through constructors: class Test { public Test() { DoSomething(); } public Test(int count) : this() { DoSomethingWithCount(count); } public Test(int count, string name) : this(count) { DoSomethingWithName(name); } } Is there a way to do this in C++? I tried calling the Class name and using the … Read more