On Saturday, 3 September 2016 at 17:05:35 UTC, Tobias M wrote:
On Saturday, 3 September 2016 at 16:32:16 UTC, ZombineDev wrote:
No you're wrong. There's no need for interfaces or for generic
constraints. It's not static vs duck typing. It's just a
method lookup issue. See for yourself:
http://rextester.com/GFKNSK99121
Ok, Interfaces and other generic methods with compatible
constraints.
But in the end you cannot do much without any interface
constraints except writing out to the console as you do in the
example.
But the main point still holds, name lookup is only done at
definition time, not at instantiation time. That's why you can
only call generic methods. Overloads don't work.
So what? C#'s generics are less flexible than C++ and D templates.
The point is that C#'s lookup does not consider only the
implemented interfaces, but also falls back to extensions
methods. If C# had ADL,
the compiler would also look for extension methods in the
namespace
of the type (in non-generic methods, when the type is "known"),
although the user of the type may not have imported the namespace.
Sum is implemented in that stupid way, because unlike C++, in
C# operators need to be implemented as static methods, so you
can't abstract them with an interface. If they were instance
methods, you could implement them outside of the class as
extension methods and there would be no need to write a
distinct method for each type. Here's an example:
http://rextester.com/PQFPC46087
The only thing missing is syntax sugar to forward the '+'
operator to 'Add' in my example.
With runtime reflection you can do almost anything... That's
circumventing the type system and doesn't disprove anything.
There's no circumventing the type system. `typeof(obj)` is barely
even reflection. You can do this with regular cast or using the
`is` expression (http://rextester.com/CXGNK69048). I used
`typeof` just because it could yield better performance.
I mean, it even "works" for types that cannot be added at all,
by just returning a default value...
? Sorry, I don't understand, what's the problem?
