A functor is pretty much just a class which defines the operator(). That lets you create objects which “look like” a function: There are a couple of nice things about functors. One is that unlike regular functions, they can contain state. The above example creates a function which adds 42 to whatever you give it. … Read more
When the compiler compiles the class User and gets to the MyMessageBox line, MyMessageBox has not yet been defined. The compiler has no idea MyMessageBox exists, so cannot understand the meaning of your class member. You need to make sure MyMessageBox is defined before you use it as a member. This is solved by reversing the definition order. However, you have a cyclic dependency: if you move MyMessageBox above User, … Read more
The error is because of the declaration: The vector contains pointers to mutable ships, but the code passes a pointer to a const ship to push_back. You either need to store const pointers in the vector: Or pass a non const pointer to the push_back: Side note: move the above function to a cpp, move it … Read more
Could you please tell me what could possibly cause a SIGABRT fault in C++?
In C++ 11 you can use std::chrono::system_clock::now() Example (copied from en.cppreference.com): This should print something like this:
If your compiler supports C++11 standard, there is a constructor inheritance using using (pun intended). For more see Wikipedia C++11 article. You write: This is all or nothing – you cannot inherit only some constructors, if you write this, you inherit all of them. To inherit only selected ones you need to write the individual constructors manually and … Read more
The & symbol in a C++ variable declaration means it’s a reference. It happens to be a reference to a pointer, which explains the semantics you’re seeing; the called function can change the pointer in the calling context, since it has a reference to it. So, to reiterate, the “operative symbol” here is not *&, that combination … Read more
I want to create an adjacency matrix for a graph. Since I read it is not safe to use arrays of the form matrix[x][y] because they don’t check for range, I decided to use the vector template class of the stl. All I need to store in the matrix are boolean values. So my question is, if … Read more
You are missing a semicolon at the end of your ‘struct’ definition. Also, needs to be
I am trying to relearn C++ after taking an intro course a few years ago and I’m having some basic problems. My current problem occurs when trying to use a friend function. Here is my code in 2 files. First: Second: The error I am getting is “multiple definition of `funct()’”. Am I using the … Read more