Let’s simplify: interface IAnimal { … } interface ICage<T> where T : IAnimal { void Enclose(T animal); } class Tiger : IAnimal { … } class Fish : IAnimal { … } class Cage<T> : ICage<T> where T : IAnimal { … } ICage<IAnimal> cage = new Cage<Tiger>(); Your question is: why is the last … Read more
There is no multi-step user-defined implicit conversion. int -> bool -> A is allowed because the int->bool conversion isn’t user-defined. 12.3 Conversions [class.conv] 1 Type conversions of class objects can be specified by constructors and by conversion functions. These conversions are called user-defined conversions and are used for implicit type conversions (clause 4), for initialization … Read more
There is no implicitly cast in Swift. Easy way of conversion in swift is using constructor of particular type. Like if you want to get Float from double then you can use Float(doubleValue) and Same way if you want to convert float to integer then you can use Int(floatValue). In your case: let intValue = … Read more
I think the lvalue-to-rvalue conversion is more than just use an lvalue where an rvalue is required. It can create a copy of a class, and always yields a value, not an object. I’m using n3485 for “C++11” and n1256 for “C99”. Objects and values The most concise description is in C99/3.14: object region of … Read more
An integral conversion never produces undefined behaviour (it can produce implementation-defined behaviour). A conversion to a type that can represent the value being converted is always well-defined: the value simply stays unchanged. A conversion to an unsigned type is always well-defined: the value is taken modulo UINT_MAX+1 (or whatever maximum value the target type admits). … Read more
The “%f” format requires an argument of type double. You’re giving it an argument of type int. That’s why the behavior is undefined. The standard does not guarantee that all-bits-zero is a valid representation of 0.0 (though it often is), or of any double value, or that int and double are the same size (remember … Read more
There is a solution. Consider the following: public sealed class AccountStatus { public static readonly AccountStatus Open = new AccountStatus(1); public static readonly AccountStatus Closed = new AccountStatus(2); public static readonly SortedList<byte, AccountStatus> Values = new SortedList<byte, AccountStatus>(); private readonly byte Value; private AccountStatus(byte value) { this.Value = value; Values.Add(value, this); } public static implicit … Read more
So why my explicit cast work, and the one inside .Cast<> doesn’t? Your explicit cast knows at compile time what the source and destination types are. The compiler can spot the explicit conversion, and emit code to invoke it. That isn’t the case with generic types. Note that this isn’t specific to Cast or LINQ … Read more
Yes. JLS §5.6.2 specifies the rules for binary numeric promotion. In part: When an operator applies binary numeric promotion to a pair of operands, each of which must denote a value that is convertible to a numeric type, the following rules apply, in order, using widening conversion (§5.1.2) to convert operands as necessary: If any … Read more
This is a consequence of the confluence of two characteristics of C#. The first is that C# never “magics up” a type for you. If C# must determine a “best” type from a given set of types, it always picks one of the types you gave it. It never says “none of the types you … Read more