There are no problems with the second version of the assignment operator. In fact, that is the standard way for an assignment operator. Edit: Note that I am referring to the return type of the assignment operator, not to the implementation itself. As has been pointed out in comments, the implementation itself is another issue. … Read more
There is no immediate answer; operators are static, and cannot be expressed in constraints – and the existing primatives don’t implement any specific interface (contrast to IComparable[<T>] which can be used to emulate greater-than / less-than). However; if you just want it to work, then in .NET 3.5 there are some options… I have put … Read more
You can’t do that. You can only provide overloaded operators for classes and structs you define — and at least one of the parameters should be of type of the class or struct itself. That is, you can declare an overloaded addition operator that adds a MyClass to MyEnum but you can never do that … Read more
The best example I am aware of is Boost.Phoenix, which overloads this operator to implement lazy member access. For those unfamiliar with Phoenix, it is a supremely nifty library for building actors (or function objects) that look like normal expressions: ( arg1 % 2 == 1 ) // this expression evaluates to an actor (3); … Read more
When both versions are available, the logic is pretty straightforward: const version is called for const objects, non-const version is called for non-const objects. That’s all. In your code sample a is a non-const object, meaning that the non-const version is called in all cases. The const version is never called in your sample. The … Read more
SQLAlchemy is a great example. For the uninitiated, SQLAlchemy is a ORM and uses Python expression to generate SQL statements. In a expression such as meta.Session.query(model.Theme).filter(model.Theme.id == model.Vote.post_id) the model.Theme.id == model.VoteWarn.post_id does not return a boolean, but a object that eventually produces a SQL query like WHERE theme.id = vote.post_id. The inverse would produce … Read more
This is well defined, both syntactically and semantically. [expr.sub]/1 (N3337): The expression E1[E2] is identical (by definition) to *((E1)+(E2)). So your expression is the same as *(q-1) = 41;, so is syntactically valid. [expr.add]/5 (N3337) When an expression that has integral type is added to or subtracted from a pointer, the result has the type … Read more
The no-cast solution is to use switch. However, you can generate a pseudo-switch using templates. The principle is to recursively process all values of the enum using a template list (or a parameter pack). So, here are 3 methods I found. Test enum: enum class Fruit { apple, banana, orange, pineapple, lemon }; The vanilla … Read more
You should define them in the library namespace. The compiler will find them anyway through argument dependant lookup. No need to pollute the global namespace.
This really depends on whether a class is going to be on the left- or right-hand side of the call to operator== (or other operator). If a class is going to be on the right-hand side of the expression—and does not provide an implicit conversion to a type that can be compared with the left-hand … Read more