unions

This question already has answers here : Closed 8 years ago . Possible Duplicate: C: Where is union practically used? I know the concept of union but I don't see the actual case in real world coding that I should use union data structure. I will be very appreciated if you guys can give me some examples or tutorials that shows cases using union properly. Thanks in advance. Where I use it constantly: parsing a configuration file I store all values in a union data type. E.g. when values can be int types or strings, I would use a data structure as follows: struct cval_s { short type; union { int

I am building a class that has a union for its matrix data, however, I can only get it compile when I do not have a name for the struct\union. However, with a higher level warning level (four on visual studio) I will a warning saying warning C4201: nonstandard extension used : nameless struct/union I looked into it, and I don't seem to be able to find a way to prevent this. Anyway possible that I know of will cause a different compiler error related to the declaration of one or the other. How can I prevent getting this warning and make it conform to standards, without just disabling the

I may be mistaken, but the basic explanation I've found has been that the union can't initialize because it doesn't know which member's constructor to call. The compiler can not automatically generate a constructor for the union. Why is the user not allowed to define the unions constructor? This would remove said issue and allow the presence of union members that have a non-trivial constructor/destructor. Also, why can't a union member have any custom constructors? The previous explanation doesn't stand for custom constructors. Update 1: Example: struct SQuaternion { union { S3DVector Axis;

I have a couple questions about how to use C++ sets (std::set) Is there a way to get the union, intersection, or difference of two C++ sets? (It's pretty easy to write my own functionto do that but I wanted to know if there was a built in function for it) Can C++ sets be used as keys in a map? Use the set_difference() , set_union() , set_intersection() and set_symmetric_difference() functions. Sets and maps support any key type that can compare. By default this means the type has operator<() defined, but you can provide your own comparator. C++ sets don't have operator<() defined and therefore

At work I've been using linux and the GCC compiler for C++11 and C++14. In some of the code at work, I've used a union to store both a reference and a pointer, as so: (Simplified to just the important parts) struct MyStruct { //Stuff union { double& x; double* x_ptr; }; MyStruct(double& value) : x(value) {} //More stuff }; I believe this code is clear, readable, unambiguous, and provides a convenient way to store references which can be shifted to something else. It provides easily understandable syntactic sugar without costing performance while improving readability. When I attempted to use